The thing that people who write off players from earlier eras (conveniently the eras before they were born and started watching) don't realize is that you can chain players from eras together, by just looking at who has played together. E.g. Cousy played in the 50s and 60s, but he played the same time as Oscar Robertson and Jerry West into the 60s. West and Robertson played into the 70s at the a young Walt Frazier towards the end of their careers. In the mid-75s Frazier played at the same time as a young Paul Westphal. In the 80s Westphal was 5 years older and played the same time as a young Magic and Norm Nixon. . In the mid-80s Magic and Nixon were joined by Isiah Thomas. In the 90s Isiah and Magic played at the same time as a young John Stockton. And so on...I have the chain below.
Statistically when you look at these guys and compare between eras, you can also end up comparing different eras of different players who didn't play at the same time as each other. Obviously there are rules changes and player aging and all those things, but I think Cousy's record both individually and relative to others he played with, who then played with others after him, stands up pretty well. The bridge players aren't necessarily there because they are all time greats, but more so as good players who can act as a relative frame of reference between eras.