Looking at a bunch of old timers' stats makes one realize how much better modern QBs are...along with shifting of the game rules. But even looking at non-rules related stats, (accruacy, not throwing INTs) they've progressed so dramatically. It's not even close really. For example, Bradshaw only threw 2 more TDs than INTs in his career and had a lifetime 71 qbr, yet is revered.
Even "the greatest to never win a SB" Marino only completed 59% of his passes, 1.7 TD:Int ratio, and career 86 QBR...respectable, but far from "great" looking vs modern guys.
Meanwhile a "3rd place" modern QB like Aaron Rodgers has a nuts 5:1 TD/Int ratio and 104 career QBR. Statistically the best, in fact. Brees had a career 97 qbr and 2.3 td:int. As mentioned earlier, both far ahead of even Elway.
Mahomes is chugging along at an incredible pace too. Burrow exploded too...see where he goes. Throw in Allen, TLaw, eventually Bryce Young...Manning.  It'll be interesting to see how far further the gap grows.
The advent of 7-on-7, qb camps, specific training, improved offensive schemes, along with pro-off rules have really progressed the QB role to a degree that older QBs now look mediocre in comparison. Not to take away what they did at the time, but it is what it is. They never had all the training and specialization and understanding these guys do.
Not starting a debate or whatever, I just find it very interesting is all. I've never looked at all those old stats and it's eye opening what a different world the NFL is now.