You haven't proved anything other than referring to mostly olympic sports that primarily require technique. You've also blatantly ignored how much bigger athletes have gotten in relation to their skill sets like the 100m record being owned by a 6'5 200lb man. If you were over 230-240+ in the NBA you were a stiff, if you have evidence proving other wise provide it. 270lb SF's like Lebron didn't exist, 6'11 270lb jump shooters like Aldridge didn't exist, 280lb PF's like Diaw that could play PG didn't exist, again, provide your evidence. The amount of ball handlers in this league that are 230+ is crazy.
You completely ignored how much bigger, faster, stronger athletes in the NFL have gotten. To say there aren't better athletes in the NBA is to say there aren't better athletes in the NFL because they literally both benefited from the same types of workouts, nutrition, etc. why are you ignoring that fact?
Bigs today would be able to take a lot of those guys out on the perimeter and break them down with ball handling or by getting wide open jumpers, in the 80's if you got blown by you could hand check and easily slow them down. It's MUCH harder to defend ball handlers when you cannot hand check, you actually need lateral speed in today's league.
245lb big men could not do this in the 80's, this 20 year old Willie Cauley-Stein is as big as Patrick Ewing but moves like a guard on defense:
Do you see how mobile bigs are? The balance it takes, the mobility, the explosiveness? Players this big and this agile did not exist back then. How many bigs in this league cannot run the floor? Even Marjanovic at 7'3 290lbs runs like the court like a deer.
Tim Duncan can't guard mobile 4's, any time you get him out on the perimeter he's a huge liability. Duncan has also extended his career by proper nutrition, proper exercise, and the medical technology we have today. If he was playing in the 80's his knees would've most likely been shot after 10 years, for sure he would not have been playing at this level. This is just another example why the NBA is better, guys are taking better care of their bodies, it leads to longer careers.
PGs are far superior it's not close with their ball handling skills
SG's are becoming combo guards, shorter, but heavier, more compact and explosive versions which gives the illusion they weigh the same as most 80's-90's guards.
SF's are ing huge, most guys are over 230+ and are very athletic, 230+ was the size of most bigs back then.
Bigs are becoming more perimeter oriented and are much better ball handlers/shooters, their mobility has increased significantly throughout the years.
Btw, Pippen never had to guard the players Leonard's guarding these days. Leonard also has 20lbs of muscle on him too lol, Pippen would probably get torn up against today's perimeter players, he couldn't even guard a rookie Iverson who tore Jordan's 55 win bulls team up.