Whether or not older people, as a rule, can perform as well as a 30yo isn't really my point -- I suppose some can, and most cannot. My point was that I don't agree that the vast majority of people who make it to old age have never become expert at anything. Older folk mostly want to talk about their youth and their grandkids, but that doesn't mean they really don't know anything other than that. They're just no longer interested (or think you aren't interested) in things they are or were experts in. Those subjects may well now be obsolete, of course; I'm not denying that.
I agree with you: what do people think happen to the brightest and the best from a few decades ago? They grow old and retire, of course. Perhaps the reason they don't sound like experts to younger folks is because they've become experts in a field we don't care about: how to view life once you have the proper perspective. After a certain point, how many lines of code or how fast your site can scale takes a back seat to how to lower your blood pressure and how to maximize your enjoyment from "simple" pleasure like family and food.
