What do you think is "wrong" with League?

I think it's a few things but some of the big ones are stuff like the game is old, the game is "too big"

With regards to the old part, this comes up in a couple ways. The game is old, thus players who have stuck with it are (in theory) going to have a lot more skill then newer players. No one likes playing with a random person who appears to have next to no idea how the game / their champion works. The game is old, thus some people will have just grown out of it. You can't expect everyone to be invested in the same thing forever. The game is old thus certain "fun" aspects from the olden days are gone. Where they really fun or where they just products of their time, the kind of stuff that if reintroduced would fail because no one wants it back they just want their golden perfect memories of the thing.

The game is "too big" Riot keeps making new champions, updating old champions, new items, updating / changing runes. Imagine for a second that the game had only 30 champions. Imagine how much easier it would be to balance everything when you only have to account for 1/4 of the current roster. Want to introduce a new champion, lets hope they tested how they fit into the game. That means test how the passive functions against AND with every other champion (don't want to find out the new support is meh with 90% of the champions but some how and are 1000% broken with them around). Repeat process with all 3 basic abilities and once more with ultimate.... don't forget to then figure in items. Imagine if items were not a thing, if champions where designed to function entirely around their kit. You want to introduce a new item into the game, better test how EVERY champion works with it and in some cases how EVERY other existing item can combo with it.

(going to update this further but got work to go to)