If you start out with a cohort of individuals across the spectrum of ability, over time many of those of lesser ability will self-select out of the pool. It is my experience (oops, see what I did there) that people rarely spend a career doing what they're not very good at. The exceptions inevitably stand out.

So, combining the winnowing of the not-very-apt with the gaining of knowledge through experience, the end result is that you have a preponderance of wise old experienced contributors.

I you are one of the younger inexperienced ones who believe they know better it's likely you'll self-select at some point, secure in your Dunning-Kreuger knowledge, and move to some career in which your high level of competence is valued more.

The counterpoint is you need time to grow wise, and there's no way to get wise without many years of experience.

That’s also true. I guess that the relative percentage of people you’d call wise increases with age.