Ironically, by "babying" or "taking care of" modern pitchers, we seem to see more injuries -- and not just with arms, but all over their bodies -- that invariably limit their innings.
But I say that assuming your quote about old-timers being "in much worse shape" didn't mean because of overuse, but refers more to their overall physiques... because anyone who actually saw guys like Mickey Lolich or Wilbur Wood (ignore the vitals reported on reference sites) knows that they were legit workhorses or other reputable mammals.
For example, after Lolich led the league with 376 IP in '71, he threw over 300 IP in each of the next three years.
Wood led the AL with 376.2 IP in '72, then led again the next year with 359.1, and followed with seasons of 320 and 291 IP after that.
The returning members of the Red Sox projected for the '23 starting rotation -- Pivetta, Bello, Whitlock, Houck, Sale -- threw 381 innings combined in '22 (including relief frames).