Compared to other companies, they let their game get out of control with features. Features they couldn't manage to keep (i.e. Dominion, champion updates, balance) weighed them down over the years.
TBH, Riot just wanted to do too much at one time and now they are so ALL over the place that I don't think a single thing about this game is balanced. Everything's either OP or broken.
The game was WAY more fun with the small roster of Champs they had since they could easier balance or cater to specific roles easier.