Reddit will make it seem like everyone hates league but there is a huge casual part of the community that isn't on Reddit that plays normals and doesn't need to stick to the meta and plays champs based on personal enjoyment or looks etc. I do this. I queue with friends and play normals and have fun. Alot of people who complain here do so probably because they are trying to climb in ranked and invest alot of time into playing seriously so OP champs or bugs are annoying for them. Also I don't know the statistics but I bet there are more unranked players than ranked players.

Plus since Riot regularly release patches and change the game they invite criticism and community feedback in their endless pursuit of balance so again people are more likely to post about a negative thing than a bad thing.

Basically I wouldn't say everyone hates league or the community as a whole does. This sub seems like it hates Riot but it's probably just because negative stuff will always overshadow positive stuff. For example the art / music department of Riot is adored by most players but they don't get praised in every post because that would be pointless whereas posts about balance issues could possibly create change.

TL;DR Reddit isn't everyone and negative stuff always overshadows the positive