Only thing I have and it means nothing is this:
The athlete is definitely better now.
The basketball players overall, IQ etc were better back then.
The guards and wings of today would be a tough defensive assignment for the players yesteryear.
There is no team who can guard the actual centers of the past because there aren't any anymore so the Kareem's, Wilt's and such would have a field day in today's game.
1) Agree. Sports movement science and fitness are insane compared to what they used to be.
2) Disagree emphatically. This is a crutch argument. The game is so much more mental now. There is so much more coaching now (each team has like 8 coaches plus a stats guy and video interns, etc.): defensive rotations, switching, sub patterns, player tendencies. These guys are also playing at highly competitive levels from early ages. It seems like the game is simpler now because it used to be more free-flowing and creative, but we've isolated what works the best now and we just hammer that into the ground... because it works the best.
3) Agree for basically the reasons of #1.
4) As we've agreed, guys are bigger and faster now, they could defend those guys adequately (they'd still be good, but they wouldn't break the game). We don't select for great post centers because they tend to be slow and doing pick and rolls for lob dunks (Drummond, Jordan, Howard, Chandler) is actually a higher % shot than backing a guy down, doing some post moves, and taking a contested hook. Or guys add a jump shot and become versatile and have post game plus a jump shot (Davis, Towns). Al Jefferson hasn't exactly lit the league on fire, but he's very skilled. The post bigs exist, they just don't have the same impact because the game has left that behind to some extent.