@Linkat,
When comparing the greats (and the eras), I look at how much they dominated against their competition and how they advanced the game. Russell, for example, helped move defensive strategy to the point where they created new rules about goaltending.
Cousy advanced the offensive precision…with his passing..no-look and behind-the-back passes. How much they changed the game and frankly sped it up.
Modern athletes are fitter and faster due to advances in nutrition and training. Rules were added to cut down the physical contact. Back in the day you had to be good but also more rugged and take some abuse under the rim and hard fouls. Much less primitive game these days.