> all the best software engineers I know are over 50
Survivorship bias? Perhaps all the bad 50-year-old programmers transitioned out or became "incompetent dinosaurs" in low-challenge areas where you can't easily see them.
If so, it's the cohort I see (the "survivors") that are routinely underestimated by tech bros. Which suggests the problem is even worse: if it visibly affects the best of the best, how bad is it for the average?