PSA: No matter what you have heard the game is balanced around proffessionals
Because it simply has to be. If it isn't balanced at the optimal level, then it isn't balanced. If it isn't balanced for top level of competition, then it wont have a competitive scene at all.
That means with a game as vast as league, certain champions will just not be very good in the middle elos, and some will be really annoyingly strong to you. It's just the reality you have to accept, sorry.
Obviously it would be optimal to have balance be equal among all skill levels, but even in the most skillful of balance hands, this isn't possible all the time.