There are hard limits to your training capability and your biological makeup influences this just as much as it influences other sports, physical or otherwise. By training you are engaging in an act of refining your biology, that's what it fundamentally is. In the case of physical sports you enhance muscle and stamina; in the case of mental sports you reorganize neural pathways in the brain.
The neurological training is not some mysterious amorphous mist that can magically be molded into whatever you'd like. It's a very real, very physical thing observable in the way of neuron connection. As you engage in mental activities your neural composition physically begins to shift and morph, but bound to certain restrictions. You can think of it as your Operation System, in which you can program and code new software but you are still fundamentally locked down to that OS.
I for one have significantly lower reaction times than most people I've played together with. Whereas they easily hit sub 200 ms reaction times I struggled to hit 250ms. Was it my 60 Hz monitor? Was it latency in showing the image or the mouse click? Was I just mysteriously tired or undisciplined every time I tried to do the test? Maybe, but would a change of setup improve things significantly? It's important to focus on the consistency.
I don't believe that people are capable of all hitting the same reaction time benchmarks consistently. Sounds kinda dumb to think that everybody is capable of being perfectly equal in that regard. You don't need to introduce cripples or sick people to observe discernible variances. This became obvious to me years ago when I taught a friend how to play competitive TF2 and in his first season he was playing two whole divisions higher than where I was.
The same logic applies to all other things. When a player has the optimal abilities straight off the bat we call this "talent", as though they tapped into some Heavenly secret or something. They didn't, they're just better by definition. It is those players/athletes/competitors who, together with rigorous disciplined training, make it to the world stages.
There is a fallacy in disregarding the biological argument, for it presupposes that all shortcomings are chalked down to purely lack of discipline, lack of training, lack of proper mindset, etc. But show me someone who's been dicking around in the competitive scene for 5000+ hours with no success only to then one day become magically good by "discipline" alone. It's far more common to witness these two subgroups: talented people who rise very fast and soon make it to the top and slow risers who eventually hit some kind of plateau and never advance further.