There are too many champions with abilities that shouldn't exist.
Few examples:
R
W
W
The issue is that these champion's overpowered abilities have made them pick/ban because of how stupid they are. It ruins the game when your champion becomes invalidated just because newer champions are far more mechanically tuned to wreak havoc in this game and cause the older champions to become outdated.
The amount of screwed up abilities and mechanics in this game that shouldn't exist are so annoying that it's unplayable, as it's not longer a question of whether your team has more skill then the other team, rather a question of "who has the more broken champions on their team."
side note: (I'm happy because I finally demoted into plat 1, it only took a 9 loss streak to do it too! I had no choice over any of the games and lost most of them due to feeders and mechanically imbalanced champions that were given the biggest roid's they could find.)