Well, the rules are simple:

Nothing besides talent should ensure you get better music schools, training opportunities, teachers, or more time to practice.

Is it fair to some are born with more talent than others? Is it fair that a 5’8” hard working talented basketball player will never be as successful as Lebron James?

Not a fair comparison. Most NBA players will fall short to Lebron James because of his brain.

https://www.espn.com/nba/story/_/id/11067098/lebron-james-gr...

Looking at the pinnacle of performance is distracting. I coach little league. Every year I see kids with amazing talent drop out or not scratch the surface of potential due to a variety of factors, most of which boils down to lack of time.

If it's beside human intervention, then yes, it's humanly fair.

The universe might not be fair though, but I'd say the universe does not give a f...

Not doable in the current economic system. Many schools would be more than willing to invest in training, should a very promising although very poor, talented kid knock at their door. But how this kid could have been introduced to classical music or any other activity requiring costly training if his/her family had to struggle every day with temporary underpaid jobs to pay the minimum necessary (clothes/health/food/school etc.)? Potential talents do exist everywhere; I'm pretty sure there are at least a dozen potential pro golfers among the homeless in any country, but they should have been grown in a moderately rich family that allowed them to start practicing at least until someone discovered them. Our economic system however is designed to make the rich richer at the expense of the poor, so I don't think this is going to change anytime soon.

I disagree. Talent is one component that gives you an advantage, but it is no guarantee for success.

Take this guy:

https://www.youtube.com/watch?v=6PyYcnXQZJY

And tell me if up front you'd have recognized his talent and given him the opportunity that you felt he deserved.

In your world perseverance and grit count for nothing, in the real world a bit of talent and a ton of perseverance will outweigh any amount of talent if it isn't coupled with a substantial amount of grit and perseverance as well.

As nice as those theories are the entrance examinations and the judges are swayed easily by things other than talent which we can not measure objectively anyway.

Fortunately instruments are affordable (for some value of affordable) and if you can spare the time then practice is the differentiator. I've seen talented musicians fail due to a lack of discipline and I've seen moderately talented people succeed through endless hard work and everything in between. Of course the talented individual with discipline will always be at an advantage. But fortunately the world is large enough that more people than that handful will get a chance and some of those will succeed way beyond our expectations.

And all that besides the fact that talent as such isn't a static thing either.

Working that out in a practical way is not simple, though. There's the rub.