With a proper training and having some kind of a coach helping them to get the mechanics and things to know behind the game, I'm sure.
Problem is that most of that people never train aim, never train movement, never try to learn any kind of smoke or nades, never train strats or play with teammates, never rewatch their demos to learn on where the mistakes are...I mean, is not as simple as I play the game and I go to the top if I play a lot, that's what I was meaning by quality of the training. Of course some people will have all those things "easier" because of his genetics or previous experiences in life.
Same thing goes for anyhting. You can get pro with proper training if you're an average guy? Yes I think so. You can be the best? Nope. But in any sport, the top 1 guy, put a lot of time an effort to get there for sure.