The animation and art is pretty decent, as is the world-building that brings it to life. The story itself is ok; not bad but nothing special either, if maybe a bit stupid. The writing and storyboarding, however, is downright terrible. It's very obvious that it was made by a studio that had only ever made game trailers up to this point. The dialogue is so overly melodramatic that it makes you just want to cringe the whole time, not to mention way too many emotional scenes that, more often than not, completely miss the mark and make you feel like you've woken up in a shitty strip mall Hot Topic. Riot should stick to making mediocre games and leave the showrunning to people who actually know how to do it properly.
Final consensus: not the worst show I've seen, but mediocre at best. Very overrated, apparently mostly by idiotic League simps who wouldn't know quality writing if it slapped them upside the head.