The biggest turn-off in LoL of mine

the fact that at LEAST 50% of the keystones on each and every single champion is unviable, tank items on anyone who's a non-tank feels SO awful and quite a few items are so bad it's laughable. You can make so many decisions that win the game for the enemy team, not only in game but before the game even starts and it has nothing at all to do with enemy champions. Like Tryndamere with any runes other than a Precision keystone and Last Stand.

And all it takes is one person to have a team lose.