Good thread, OP. It's really addressing the change in technology, which is far bigger than most realize. And I'm not trashing my all-time favorite player McEnroe by saying he'd get swept by Serena. I'm trashing the technology. As I said, I was shocked when Mac played Roddick so tough when he was 54 and Roddick was 32. So yeah, we can laugh watching old film. But the technology was a joke back then.
Here's one of my very favorite videos ever that explains the differences in technology across several sports, along with several other factors as to why athletes have continued to completely destroy records across time. When I first saw it 9 years ago, I was blown away. But it makes complete sense.
If you don't have 15 minutes to spare, I'll highlight a few of the main points, regarding technology.
The world record for the most miles bicycled in one hour(as of 2014, the year this video came out):
1972: 30 miles and 3774 feet, or 30.71477 miles
1996: 35 miles and 1531 feet, or 35.28996 miles(with a drastically better bike, 14.895% improvement over 1972)
2014(with same bike technology as 1972): 30 miles 4657 feet, or 30.882 miles(0.53% improvement over 1972)
Note: The women's record using modern bike technology went 30.605 miles, which is extremely close to the man's record on a 1972 bike.
Jesse Owens with crummy track finishes last in the 2013 World Championship 100 meter race; finishing 14 feet behind Bolt. With a modern track, mathematicians said he'd finish in 2nd place. And he'd be less than a stride behind Bolt.