Risk and Reward

In a game where there are over a hundred champions. Only a few are actually viable for most people. (key point, "most people")

If you watch the Patch notes you'll notice a trend. 80% of the time the exact same champions are cycled through buffs/nerfs. On top of that, then you get items buff/nerfs that narrow the field of champions even further.

Like , zed is stupidly broken because he isn't high risk high reward. Yeah he's an "Assassin", but he has one of the safest poking ranges, he can dive a 5 man team and simply click "r" and instantly get away (especially if he builds movement boost items), and now he has a new toy that is pretty much an echo of his ult . Literally an item specially made for zed. Literally his ult will nowl kill you if you manage to get away from a zed ult with only a few Hp.

Riot, they're hundreds of champions, act like it, stop building meta's that force players to use only certain champs. (You can try breakin the meta but it doesn't really work all that often)