Just to be clear, because I may have been the one that started this, I never said, or even meant to imply, that Brady isn't the GOAT, or wasn't tough as nails. But there's no way to dispute that what qualified as roughing the passer in 1983 is very different than what it was in 2013. There's no way to dispute that what DBs could get away with in 1983 is very different to what they could get away with in 2013.
Brady is the GOAT, and for what it's worth, Steve Young is my favorite even though Montana was better. I was only speaking to what I see as the futility of making statistical comparisons across eras.
Yeah, I don't think anyone is disputing that at all. It's a claim that makes total sense. When Brady played in, say, 2004, the rules were still much more like the old rules (they'd change after that season), and we see what Brady did. Let's compare 2004 Brady to some normal years from other great QBs who played a few years earlier:
2004 Brady: 60.8%, 3,692 yds, 7.8 y/a, 28 td, 14 int, 92.6 rating
1996 Elway: 61.6%, 3,328 yds, 7.1 y/a, 26 td, 14 int, 89.2 rating
1983 Montana: 64.5%, 3,910 yds, 7.6 y/a, 26 td, 12 int, 94.6 rating
1991 Marino: 57.9%, 3,970 yds, 7.2 y/a, 25 td, 13 int, 85.8 rating
1989 Kelly: 58.3%, 3,130 yds, 8.0 y/a, 25 td, 18 int, 86.2 rating
Obviously all these guys had worse years than this and better years than this. The point is, Brady's passing numbers if he played in the same era as Elway/Montana/Marino, etc., would probably have looked very similar to those guys', and we have an idea that this likely would have been the case because Brady did play a few seasons before the rule changes came into play favoring the offense and passing game.
He probably would have had some years worse than this, and also some bonkers years where he threw for 4,300 yds, 30+ td, and fewer than 12 INT, but it likely wouldn't have been an every year kind of thing.