This applies to the longevity/productivity of all players, obviously, and not just QBs...
But advancements in field technology alone somewhat skew the odds in the favor of the modern player.
As far as I know, Jim Kelly played on what was basically astro turf over concrete at Rich Stadium.
I think of all players, including Kelly, being slammed into the street with a rug over it, basically, 10,000 times...and I cringe.