Eh, that’s pretty anecdotal, and there were genetic freaks before. Nolan Ryan and Kareem Abdul-Jabbar both had long, highly productive careers. I’m not saying sports medical science hasn’t improved a lot, but it’s not like there simply weren’t late 30s or early 40s people competing at a high level. I suppose you could argue that the games are more competitive these days, and that if not for medical improvements, people would otherwise have had to retire earlier.