Article 1: The GTM Reality Gap -- Why Effectiveness Collapsed, and CAC Exploded in the World Scott Brinker’s 2026 Report Describes

Scott Brinker and Frans Riemersma just published their Martech for 2026 report. It landed as Proof Causal.ai and Fiduciari.ai were putting finishing touches on our joint year-end GTM Effectiveness Report. After reading theirs, we saw a unique opportunity to vector our findings into theirs, all while acknowledging the incredible contribution they have made over the years to GTM.

Both reports land at a moment when GTM organizations are struggling to make sense of their own decline. The report describes a landscape in which deterministic assumptions are giving way to probabilistic systems, linear workflows are dissolving into nonlinear buyer behavior, and generative and agentic AI are changing not only operations but the very nature of buyer perception and decisioning. Scott’s contribution is a map — a clear description of the shifting terrain.

What his report does not attempt to do, and what this series addresses directly, is explain why GTM performance has deteriorated so sharply during the same decade that Martech matured, AI reached ubiquity, and GTM teams became more sophisticated than ever. If the tools improved and talent rose, why did outcomes fall?

Proof’s GTM Effectiveness Report 2025 provides the empirical answer: GTM effectiveness has not declined as much as it has slowly collapsed.

We have had access to an enormous reservoir of GTM data from companies in the midmarket and the enterprise categories, enabling us to see the causal relationships at scale. For years, it has been something like a slow-motion car crash. Moreover, it has often felt as though we were one of the few watching.

In 2018, before Covid, B2B GTM effectiveness stood at 78 percent.
By 2025, it had fallen to 47 percent.
The line never reverses. It only steepens.

But something else happened during this period — something even more economically devastating than the collapse of effectiveness. Customer Acquisition Cost (CAC) spiked across the industry, and the recoverability of CAC — what we have long called the “CAC Loan” — has disintegrated.

This article, the first in a five-part series, examines the people and mindset dimension of the collapse: why GTM professionals continued believing in deterministic models long after the world had become probabilistic, why their tools amplified those beliefs, and why Sales in particular suffered a structural implosion driven not by capability decline but by market physics GTM was unprepared to confront.

By adding the CAC and Sales-effectiveness mechanics explicitly, we can now see the GTM collapse not merely as a philosophical mismatch, but as a systemic economic breakdown caused by outdated beliefs applied in a volatile marketplace.

1. The End of Stability — and the Mental Models Built for It

From 2005 to 2018, GTM professionals operated in a period of relative environmental stability. Buyer behavior shifted, but gradually. Channels multiplied, but not explosively. Marketing evolved, but largely within a predictable logic. Martech grew, but its primary purpose was efficiency and orchestration, not epistemic transformation. Even the financial landscape — capital availability, interest rates, buyer confidence — behaved within a predictable range.

In such an environment, GTM leaders reasonably believed that the world was deterministic enough for their models to be true. Buyers progressed through stages that could be influenced. Pipeline behaved like a flow system. Sales cycles, while variable, were anchored in norms. Deal sizes behaved within ranges. “No decision” was a minority outcome. Forecasts were useful because historical patterns were reliable.

These conditions allowed GTM to flourish under a worldview that assumed:

• internal actions drove external outcomes,

• buyers followed linear logic,

• historical patterns would persist,

• attribution could reliably infer impact, and

• scale could overcome friction.

GTM’s logic model became not only a framework but a form of professional identity. People were trained, promoted, and celebrated based on their mastery of this deterministic worldview.

Then the world changed.

2. The New Marketplace Is Not Merely Different — It Is Incompatible with Old GTM Logic

Beginning around 2018, and accelerating through 2020–2025, the marketplace underwent a structural transformation. Buyers became nonlinear in their evaluation cycles, shaped increasingly by peer networks, procurement skepticism, economic volatility, and AI-driven research. Macroeconomic turbulence — particularly interest rate uncertainty — reshaped capital allocation, increased internal scrutiny, and suppressed willingness to commit.

The environment shifted from deterministic to probabilistic, from internal control to external dominance, from predictable patterns to volatile signals, from linear journeys to chaotic networks of influence.

But the most consequential shift was this:

Buyers dramatically reduced their rate of decision-making.

This single change — buyer decision paralysis — sits at the center of the GTM collapse.

And it hit Sales first, hardest, and fastest.

3. Why Sales Effectiveness Collapsed Faster Than Marketing Effectiveness

Our dataset reveals something critically important: Marketing effectiveness has declined, but not as catastrophically as Sales effectiveness. That has fallen off a cliff — and this is the primary accelerant of the overall GTM decline.

This was not about professional competence. It was a mathematical failure.

Here are the marketplace changes that reshaped Sales performance:

• Deal Velocity has ~doubled

What once took 60–90 days routinely now takes 120–180 days — or more.
Sales labor throughput is cut in half even when effort remains constant.

• Year-1 Deal Size has fallen by more than 60 percent

Even successful deals produce far less economic return. This drastically reduces CAC recoverability. Remember, CAC is a short-term loan designed to secure revenue. When everything takes longer to secure a smaller deal, and more deals close without a decision than ever before, the “CAC Loans” go pear-shaped.

• “No decision” outcomes now reach 73–78 percent

This is unprecedented. That means that about four out of five deals produce zero return — meaning Sales investment cannot amortize across outcomes. It also means that the reality of this metric is twice as bad as everyone thought it was in late 2024.

These forces do not merely reduce Sales effectiveness. They mathematically destroy it.

When:

• fewer deals close,

• those that do close take twice as long, and

• those that close are dramatically smaller,

Sales productivity collapses — no matter how talented the team is.

This is the causal hinge:

Marketing decline is additive. Sales decline is multiplicative. That’s why GTM effectiveness has not simply declined — it has accelerated downward.

4. The Hidden Story Behind Rising CAC: A Collapse in Causality

The industry’s spike in Customer Acquisition Cost (CAC) over the last five years has been misdiagnosed as a marketing budget problem or an efficiency issue.

But CAC is not just a marketing metric. It is a system performance metric, incorporating:

• Marketing cost to generate pipeline

• Sales cost to process and convert pipeline

• The time cost of a lengthening cycle

• The opportunity cost of no-decision outcomes

• The revenue yield of smaller deals

When Sales cycles double, CAC rises — even with flat budgets.
When win rates collapse due to no-decision outcomes, CAC rises sharply.
When ACV shrinks, CAC payback lengthens automatically.

This is the CAC truth most companies do not understand:

CAC goes up not because GTM is undisciplined but because the modern marketplace doesn’t support vendor expectations.

The CAC Loan metaphor captures this perfectly.

Historically:

• 9 months → healthy

• 12–15 months → acceptable

• 18 months → concerning

Today:

• 18–30 months → common

• 36+ months → widespread

• indeterminate → increasingly normal

The CAC Loan no longer works because:

GTM pours money in at the front end.
The market returns revenue too slowly — or not at all.

This is the economic root of the GTM crisis.

5. Internal Coherence Masked External Collapse

Despite these macro shifts, GTM internal dashboards still looked “healthy”:

• pipelines remained full,

• MQLs rose,

• engagement increased,

• attribution charts looked orderly,

• predictive models still produced numbers,

• activity logs remained dense.

Internal signals were coherent, meaning they reflected expectations. This created the illusion of competence in a system that had already lost relevance.

Sales and Marketing were navigating using maps from an era that no longer existed.
Martech amplified this illusion by providing reports and dashboards that were internally clean and externally meaningless.

Thus:

• GTM believed it was improving,

• while effectiveness was collapsing,

• while CAC was exploding,

• while Sales productivity was evaporating.

This is not mismanagement. It is epistemic drift — a loss of understanding of how the system actually works. For whatever it’s worth, GTM is not even close to the only functional teams struggling with this.

6. Why Human Expertise Failed to Update: GTM’s “Professional Religiosity”

GTM is one of the most culturally cohesive functions in the enterprise. It has rituals, orthodoxies, sacred frameworks, and shared narratives that shape professional identity. The funnel. The MQL. The buyer journey. Attribution models. Pipeline stages. Forecasting logic. These were not merely tools; they were articles of faith in a system GTM professionals believed they understood.

When the world shifted, these beliefs did not update.

Instead, we saw:

• optimization of outdated funnels,

• refinement of attribution models that no longer reflected causality,

• blind investment in automation,

• massive pipeline inflation to compensate for win-rate collapse,

• reliance on historical forecasting despite historical irrelevance.

In other words, GTM’s worldview became a form of professional religiosity — internally coherent, emotionally comforting, and no longer reflective of Reality.

This is why talent did not prevent decline. The decline occurred because talent operated faithfully within a worldview the marketplace had already invalidated.

7. Martech Did Not Fail Despite GTM Logic — It Failed Because of It

Scott Brinker’s report highlights an important truth: technology is evolving rapidly, but it cannot replace flawed logic models.

Martech did not modernize GTM. It industrialized GTM’s outdated worldview. More specifically, the deterministic machine that many VC’s envisioned for GTM in 2005 was a total bust because it ignored a simple reality: the Marketplace, and the People in it, are all part of a radically probabilistic Open System. Not only did it not work, it was never going to work. “Scale to Success” wasted more investor money in twenty years that perhaps any other growth strategy, and the fact that some companies got lucky misses the point entirely.

Technology encodes assumptions:

• automation encodes linearity,

• CRM encodes flow logic,

• attribution encodes correlation,

• predictive scoring encodes pattern stability,

• content engines encode repetition,

• AI encodes imitation.

These technologies scaled a logic model that no longer corresponded to the environment.

Thus, Martech did not rescue GTM. It accelerated GTM’s collapse by scaling misunderstanding faster than humans could detect it.

This is not a failure of technology. It is the failure of the logic that technology inherited.

8. The Path Forward Requires a New Commitment to Reality

Article 1 ends where the rest of the series begins:

GTM will not recover by:

• running more playbooks,

• optimizing funnels,

• tuning attribution,

• improving enablement,

• buying more Martech,

• or hiring more SDRs.

These are optimizations of a model the world has already left behind.

The only viable path forward is to adopt a new logic model — a causal model — one that reflects:

• external dominance,

• volatility,

• nonlinearity,

• confounder influence,

• lag dynamics,

• buyer decision entropy,

• and the collapse of deterministic assumptions.

Only then can GTM leaders understand why effectiveness fell, why CAC exploded, why Sales productivity collapsed, and why Martech scaled a worldview that could not survive the environment Scott Brinker has so accurately described.

Articles 2–5 explore how to rebuild GTM on causal truth:

• Article 2: The collapse of deterministic process logic

• Article 3: How technology scaled the wrong model

• Article 4: Why GTM misalignment is now a fiduciary risk

• Article 5: The Causal GTM Operating System

The maps have changed.
The terrain has changed.
GTM must now change with them.

On to Part 2!