Originally Posted by BadBaronRudigor

Again, you seem not to recognize that somewhere between age 26 and 28 there is a major dropoff for most players of this type in rebounding in particular.

As comps, I looked at the first 3 names other than Erving on the GOAT list (helpfully, they all start with B, lol).

Bird: Rebound Rate to age 26 = 15.9, BEST year thereafter 14.7.

Baylor: R/G to age 27 = 17.5, at age 28 dropped to 14.3, BEST year thereafter 12.8

Barry: Rbr to age 28 = 9.2, age 29 8.7, thereafter BEST year 7.6
(special note: Barry is missing his age 21 and 22, his best r/g but before RbR calculated so this difference even more pronounced) (special note 2: Notice for Barry that I included age 28 because that gives his a year back in the NBA . . . where his RbR was appreciably HIGHER both the 2 years before and the 2 years after than any of his years in the ABA so the league wasn't the answer here)

There will certainly be exceptions to this general trend but this provides anecdotal evidence that similar players' games DO shift in this manner based on age, not necessarily on "lesser competition"
Erving is more typical than not in this respect from my observations of players over the years and backed by a quick sampling of evidence . . . you can probably expect a similar pattern from McGrady