Actual Issues in League
Too much overlap, lack of items, and pigeonholing. Let me explain each:
Overlap: tons of overlap exist between champions , runes, and items. Too many objects doing the same thing means only one of them will be used.
Lack of Items: not enough real item diversity and items that offer counterplay. For example, an item that makes one immune to incoming disables for like 3 seconds. Not enough variance in AP either.
Pingeonholing: Feels like Riot forces you to play the game a certain way by purposely overnerfing things they don't want you to do. Like adding a bunch of useless stats on support items, for example, so not even supports want to build it almost.
I'm sure you all have different opinions on the matter