Larger competitive scene (Con: With competition comes awful noobs and a very toxic community)
Easy to pick up, hard to master
Everyone else seems to play it
To counteract some points on why people like Dota 2 more:
It's graphics: well, League is made to look the way it is, they're aiming for the cartoony shit
Takes more skill: yeah, go play chess with people then, Mr.LeetGamer, people love simplicity, look at FPS games and Flappy Bird.
No places to hide in like a little bitch: Guess what, this little bitch is gonna outplay you from hiding.
Gotta pay for champs: I'll have to give you that, it does suck. But Riot loves their money.