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.

Traditional funnels jump from a marketing signal (like an MQL) to an opportunity, creating a blind spot. They miss the 'Engagement' period of initial interaction and the 'Prospecting' phase of active sales pursuit. Ignoring these stages makes it impossible to diagnose performance issues or identify improvement levers.

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 marketing funnel's resilience isn't just inertia. It's systemically reinforced from both ends of a marketer's career. Universities teach it as a foundational concept, and leadership (CEOs, boards) demands its simplicity for reporting, leaving practitioners in the middle unable to drive change without significant career risk.

With buyers completing nearly 80% of their research using tools like Generative AI before vendor contact, the linear funnel is dead. Traditional metrics like MQLs and SQLs are meaningless. Go-to-market strategies must be rewritten to influence buyers during their independent, non-linear discovery phase.

SaaS companies often use the traditional top-down sales funnel as their mental model. However, this model is fundamentally flawed because it ends at the 'close' and completely ignores the recurring revenue component, which is the lifeblood of SaaS. The 'bow tie' model is a more accurate representation.

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.

Direct-to-consumer (D2C) brands often excel at straightforward messaging and simple user journeys. B2B marketers should emulate this clarity. Complex B2B products often lead to jargon-filled copy and convoluted website flows, creating friction that a D2C mindset can help solve.