Genes are a lot more complicated than that. Unless you get some really blatant genetic problem, like Down Syndrome, there's a very heavy environmental component to how you turn out. And that's exactly what you want, isn't it? You want your life not to be predetermined, or even predictable -- and that seems to be the way things really are!
Of course, some people do wind up with, say, a genetic predisposition to alcoholism or depression. But if you have something like that, wouldn't you like to know about it? If you know that you're predisposed to alcoholism (or whatever) then you can do something about it, instead of just letting it happen to you.
Apologies, but this attitude is quite annoying: "As long as you're healthy and a hard worker, you too can be a genius! It just takes time!"
If anyone bothered to try to answer the question "do genetics matter much?" by examining real-world prodigies, they would be forced to conclude "Yes, genetics are equally important to upbringing/environment".
Read through this, then claim genetics don't matter:
"This was Richard Feynman nearing the crest of his powers. At twenty-three ... there was no physicist on earth who could match his exuberant command over the native materials of theoretical science. It was not just a facility at mathematics (though it had become clear ... that the mathematical machinery emerging from the Wheeler–Feynman collaboration was beyond Wheeler's own ability). Feynman seemed to possess a frightening ease with the substance behind the equations, like Albert Einstein at the same age, like the Soviet physicist Lev Landau—but few others."
— James Gleick, Genius: The Life and Science of Richard Feynman
Fun fact: Feynman mastered Calculus by age 15. He didn't just learn it; he derived it himself.
I'm also irritated by the inaccuracy of that attitude, which is why I never expressed it. Of course genetics are a big deal. They just aren't the only thing, which was the subject at hand.
Of course, some people do wind up with, say, a genetic predisposition to alcoholism or depression. But if you have something like that, wouldn't you like to know about it? If you know that you're predisposed to alcoholism (or whatever) then you can do something about it, instead of just letting it happen to you.