Jon Miller, who helped popularize the MQL, now compares its linear funnel to the geocentric model of the solar system. He argues it was a once-useful simplification that no longer reflects the complex, nonlinear reality of B2B buying, as it ignores the most important, untrackable parts of the journey.

A critical insight from Refine Labs is that what marketers call a "funnel" isn't a map of customer behavior, but a framework for an internal sales process. This common misinterpretation leads marketing teams to incorrectly believe they are modeling the buyer's journey when they are merely tracking their own operational stages.

"Path dependency" is when past decisions, like adopting the MQL waterfall, constrain current strategy even though the market has changed. GTM teams get stuck trying to optimize a legacy, linear framework for today's non-linear buyer, preventing real innovation and ensuring suboptimal results.

The inertia behind outdated metrics is a quantifiable problem. A poll of senior marketing leaders found their biggest issue is that leadership is "obsessed with MQLs and they don't know anything different." This suggests the primary battle for modern measurement is often fought in the boardroom, not the marketing department.

The marketing funnel survives not because it's accurate, but because it's a memorable piece of "intellectual property." In a world of information overload, the human brain gravitates towards simple, easy-to-understand concepts. The lack of widely accepted, equally simple alternatives in B2B marketing ensures the funnel's continued dominance.

Academics defend the funnel as an aggregate snapshot of a market's proximity to purchase, not a literal customer path. However, this theoretical definition is irrelevant because practitioners use it as a linear tool for micro-optimizations (e.g., MQL to SQL conversion), which is precisely why it fails to reflect the non-linear reality of modern buying.

Marketing leaders often sense that attribution models are broken, but they lack the financial language and models to prove it to leadership. The key challenge is moving from "feeling" that a model is wrong to "articulating and demonstrating" why with a cogent financial argument.

Companies stay stuck in failing models for three reasons: 1) The system rewards controllable but ineffective activity (more calls, more MQLs). 2) Leaders fear the perceived risk of foundational change. 3) A culture of urgency favors quick tactical fixes over addressing deep, systemic issues.

In subscription or repeat-purchase businesses, the customer relationship begins at the point of sale, it doesn't end. The funnel metaphor is limiting because it ignores the crucial post-acquisition phases of adoption, expansion, and loyalty, where most value is created.