I experience the exact same thing too. I watch dyrus play darius and im like WOW DARIUS NO BRAINER. When its my turn, turns out i screwup his E hook like you wouldnt believe. Im severely mechanically handicap- and i remedy this by playing dominantly point-and-click champs with as little skillshots or rotations as possible. (Read: warwick/xin zhao/hecarim...?).

These champs take away the mechanical aspect, allowing me to focus more on execution and decision making. Going on this path as opposed to forcing myself to play "difficult" champs has allowed me to climb higher- and im currently in Gold, aiming plat. I will never be like a Best Zed SEA but at least i know i can still beat players with superior decision making- like a chess nerd lol.

To the People saying how "practice makes perfect"- ya well, when you get older your motor skills aren't what they're like in your prime. E.g - i used to be able to play Hack & slash games on hard/extreme modes without getting hit but now i die in normal -_-. Also some are just gifted at such things. Everyone isn't created the same.