Yeah I definitely agree with that. Henderson would've been an allstar with his athleticism, coordination, drives and dunks. Put Chris Kaman from a couple years ago back in the 60's and he would've been scoring 30+ppg. He has great moves inside but now every team has a 7 footer to defend him with. He would've been as dominant as George Mikan. In today's game he's a role player. The bad players now are much bigger, faster, stronger and more knowledgeable than players back then. They have teams of coaches and work year round. Back then professional athletes smoked, drank and worked jobs on the side for money. Now days players are far better shooters too. In the 2014-15 season there were 33 NBA players who shot 85% or more on FT's with 100 attempts. 50 years ago in 1964-65 there was ONE, Larry Costello.
Now you take some of the greats from back then and put them in a modern training environment it would've been interesting to see what that would've done. Those players didn't have the staff, trainers or coaches that modern players have. Especially players with injuries; there was no ACL reconstructions back then. If you got hurt you just had a bad knee and that was that. So modern players have the luxury of those advances.
There will never be an answer to these debates, but we all have our opinions.