The teams are much more sophisticated than the average fan thinks. Atleast a lot of them are, they track pretty much everything all the way down to how many times a guy rubs his balls on the court.
Guys slip through the cracks in every sport. Doesn't mean't the entire process of talent evaluation is flawed.
Like I said sports is much more of a meritocracy than you think. There aren't too many guys balling out at the local Y who would otherwise be dropping 20 on Deandre Jordan out there.
Unless you get a crack habit, if you're 1 of the best bball players in the world you are probably not slipping through the cracks. Especially nowadays, if your in the Congo and can ball they'll find your ass.