You don't see this in crucial roles in sport, for example, where athletes who once possessed the talent for glory can't hide it when they perform poorly or are past their prime.
Thankfully, there are no deteriorations in performance for physical ability alone in tech, rather, mental abilities improve over time (Except for roles where the grind is important), but in the early tech days, "Winning" meant creating things that were measurable and clearly showed that.(Mostly at least, there will always be exclusions to the norm).
The past decade and a half have been near unbearable with the progressions in tech culture at companies resembling what internet memes on corporate culture are made of. Heavily verbose emails and pointless discussions of low intellect for the most minor of issues or features.
Power is concentrated not in software engineering ability, but in the boardrooms of clueless MBAs and while you say it isn't about that, what i see indicates it is largely because of that.