I enjoy viewing clips of classic college football games from the 50’s and 60’s. My initial impression is always how relatively small those players were compared to today’s behemoths.
To further buttress your point:
If you can, watch a video of the 1958 NFL Championship Game between the Giants and the Colts. Not only were the players tiny compared to today but their conditioning compared to today was so poor they could barely stand up at the end of the 4th quarter.
But, we’d have to expect some improvements after half-a-century.
My $0.02 worth of modest proposal:
Change the substitution rules and make say, four or five players play both offense and defense. They can still get substituted in & out, but it would have to be over a period of time.
Then you’d see a different type of athlete instead of a behemoth.
As I said, just my $0.02.