It's not entirely true that previous capital expenses are a permanent buff/debuff. The capital resources Mercedes have all have a finite competitive lifetime, and are going to become progressively less of an advantage over time. The next capital project Williams takes on, if they do it effectively, will result something more effective than what big teams already built due to being newer and being built on more modern tech.

It's true that right at this moment, big teams are flush with up to date capex projects from the pre-cap era, and so can focus their resources on car development rather than capital projects... where small teams have tough prioritization decisions to make. But that won't last forever, and within a few years those big teams are going to have a painful experience of reintroducing capital projects that reduce their car development budget.

I'm sure this is frustrating for team-principals that are in the thick of an infra rebuild, staring at competitors who are starting with the job done. But 5 or 10 years from now, the steady rate of capex refreshment will be what matters, and the one-time pre-cost-cap injection will no longer mean much. And realistically, this is the most the cost-cap can achieve. You can't delete the advantage from 30 years of massive spending overnight... all you can really do is stop the bleeding and let time run its course.