Thing is those "rich kids" have similar levels of athleticism if not better than those who come from less fortunate backgrounds now. Look at a guy like Zach Lavine, I think his dad played in the NFL, nice background as far as financially and he can jump out the gym with the best of them. At the end of the day you still have to be good, just being rich ain't gonna get you to not only make the league but stick for a good 10 years or so.
Alot of cats in this thread are focusing on the "rich" part and not on what you just pointed out...a lot of NBA nikkas are coming from parents who were elite athletes. Gone are the days where you're a NBA player and your pops was a garbage man or worked at a plant. Mitchell, Tatum, Brown, Currys, Thompson, Booker, Wemby, Miller, Morant, Doncic, Ball, Irving, Alexander, Jalen Williams, and many more have parents who competed at HS, collegiate and/or Pro/ international level.
its very rare nowadays you get a guy like Draymond, Cam Thomas or Edwards who are from the hood, had unremarkable parents, went to public HS (for a few years at least) and still made the league.