I agree, but we can "destroy" a top talent that can develop into a top level Serie A player.
Also
I'm a firm believer that both nature and nurture influence human behavior, let alone achievement. It is actually quite proven.
Obviously, you can use extreme outliers as counter example for argument purpose (like mentally retarded or genius) that for some people the external factor (nurture) cannot change much in a relative manner to the rest of the population, but it still cannot deny the fact that NOT everyone that are gonna make it are still gonna make it anyway, regardless the what external factors are there.
You kind remind me one of the reasons why I like Mancini a lot back then, cause he does try to develop some players that are somewhat on the fence of making it or not, I would even consider JC, Maicon as one of them, (maybe or maybe not Balotelli), the questionable ones are Luis Jiménez, Pelé, even on his second time he was willing to try Alassane Traoré, and you can see at least some of them might work out, at least to the level of a utility player for Inter.