In certain areas, hours might be enough, but not always and everywhere.
Chess is a good example. I've seen a 12 year old kid at a chess competition wipe the floor with dozens of much older players (people in their 40's, 50's, and up), who've been playing chess -- obsessively -- their whole lives.
This 12 year old kid has been playing chess for maybe 6 years (let's say 8 years maximum), but he totally crushes others who've played 40 or 50 years or more. Chess can be very addictive, and a lot of people spend virtually all their waking time playing it, for decades on end, studying, competing, yet that's not enough, and they can be easily beaten by someone much, much younger than them, who's put in only a tiny fraction of the time and effort they have.
I've also seen a 10 year old kid, who was really hyperactive and distracted when he played, always looking around him at everything but the chessboard, apparently interested in anything but chess. His mother sat next to him, and had to struggle to get his attention back to the board whenever it was his move. Yet he played at a high level against people much older than him. Again, he really couldn't have put that much time in to it, no matter how interested he was in it.. and he clearly wasn't that interested.
Chess is one of those fields where prodigies are relatively common, especially compared to fields like poetry that really do require a lot of life experience to be effective. The kids I've described are not that rare. It happens even at the highest levels, with Bobby Fischer being the archetypical example (becoming the youngest grandmaster at 15 and winning the US championship at 14). These days chess prodigies are even more common than in Fisher's time, thanks to computers and the internet. Still, whatever happens with them is not explained by the hours they put in to the game alone, as many people put in many more hours and much more effort than they do and still fail miserably.