The point is, training is crucial for developing to become a great player, but the best players, the highest level play will be defined by "genetic advantages", you can go closer to them, but if they keep on training you won't be able to achieve what they can, but you still can achieve awesome things.
So yes, high level play can be achieve by both nurture and nature (although being naturally good still requires you to practice), but the highest level play is defined by nature over nurture (knowing that practicing is still required).
*Edit*: I say this because high level play can be considered to, for example, include people that aren't as talented as the best players (Niko, Cookiezi, rrtyui), but still are at the top 1000 or 500 (like me for example, I guess I can be considered high level player for some people, or at least above average idk, although I don't consider myself a high level player)
My vote still goes to Nature