Again, you’re really stuck on this. Maybe players aren’t bigger, I know PGs specifically ARE bigger, but whatever, have that one. Stronger yeah probably not, but brute force isn’t emphasized in this league like it was back then. Plenty of guys in that era were on rosters mainly for strength and enforcement, those guys would be playing in Europe now. 
Players are 100% faster and quicker and more skilled though. The top end athletes are probably the same numbers wise, for example David Thompson and Keon Johnson have the same record max vert. But, the depth of athleticism is higher. There are more tier 1 God-Level athletes than there were, and there are less below average athletes.