Guys are quicker, faster more athletic and defense is way more advanced. This is a pretty well known fact. Defense was hardly played in the 80s.Hence why game scores were at a well over 100 points in the 80s while the pace now is is about 90 points. Pls dont confuse cheap shots or taking hard fouls as playing good defense.
Hand-checking was allowed back then, perhaps your too young to recall? MJ would have been quicker without it too. Some of the players today would whine if they got hand-checked or completely neutralized with a build like Curry's. Getting rid of that really helped the offense. I can see a lot of guys having trouble with hand checks today. Getting rid of that really help guard production.
I think the no charge circle gave more power to the bigs too. They basically invented that to allow Shaq to charge over people and to compensate for his lack of range.
Overall, I can't argue that the athletes today are not better athletes. Skill wise though it is the opposite. I think guys in the 80s were more complete players, in terms of skill. There are some really complete players today but specialization has really become the order of the day.
Bigs back then were way more skilled than the ones today. They had post moves and a lot of them could pop out. There are guys who can do that today, but you also have a lot of guys who can only dunk. As crazy as it sounds, I think the league had more size back then in seven footers than today.
Three point shooting has vastly improved today. That is not up for discussion. Bird was a great three point shooter, but he hated that shot. I would want Larry in the three point contest or to take a final shot but there are several guys I would pick over him in terms of three point production in a game.
Toughness wise I give to the 80s guys. They played without Air conditioning and modern amnities. They played hurt a lot more too.