Nobody will ever come CLOSE to a skill ceiling so the discussion is pretty pointless, think about it. As a scout, you would need to hit every single shot for maximum damage. Every single shot. If you think anyone is remotely close to this then you are mistaken. As sniper, you would need to never miss a headshot, ever. You would also need impeccable gamesense and never get caught out of position, not even once.
That being said, the best players in the game can potentially be the best at every class, so the key to becoming the best is not understanding one class to its maximum potential as the thread may have you believe, but understanding every class and the overall flow of the game. To be the best at any class you require good aim, good movement, and good gamesense, there's no way around it.
Fin.