TLDR: the vast majority of markets are demand-bound. So if you are producing marginal supply, you're are simply hurting everyone and at best will do as well as the others.
Unless, of course, you cheat, which is what these connections do.
Needless to say, there is a global fiction that everybody seems to believe that this is not true, both on the left and (especially) on the right. It is so ignored on the right that this situation is actually left out of economics education.
I'm a CFA, I have grades, never got a look in for fund manager jobs. Pivoted to computing at the age of 30 where I "look the part" or whatever.
Don't kid yourself about this stuff. I'm not from an underprivileged background by any stretch of the imagination and nor do I have any time for socialism and socialist posing.
Young Dennis will get a game somewhere and put up compelling numbers and will likely get to the NBA. The equivalent can't be said for young potential fund managers who won't get a chance to impress. Positive discrimination is not the answer to this, but neither is the ostrich strategy.
OTOH, professional sports leagues are about winning intense competition, and skill is much more important. Even then, coaches and owners play favorites.
It's not a binary system, it's a spectrum, and professional sports are towards one end of the spectrum and hedge fund management and VC founding are towards the other end.
Even if J. Random put all their training into building and managing relationships it would likely not amount to anything of note. (They will have fewer resources and be excluded from some social circles.)
There are many necessary components of huge success.