Literally every game forum is like this. People go on Boards to give feedback when they're unhappy with something, not so much when they're satisfied, which to anyone browsing here creates the impression that nobody enjoys playing the game, even if the opposite is more true.
That much is fine, though: Gameplay is intended to be a place for players to point out issues within League, try to provide as much information as to what the problem is, and work towards drawing up potential solutions, and more generally to work with Riot to improve their game and give a pulse on its current state. The problem, though, is that the culture on Gameplay is so toxic, hyperbolic and generally noisy that the board only rarely ends up contributing positively, which is why there's now a separate Dev Corner for Riot to talk about issues, and Nexus articles for them to share their design philosophy. Part of the problem is that forums in general tend to stagnate and develop their own group mentalities over time, since the most influential players there tend to be the ones that stay there the longest and produce the most posts, but another big issue is that Gameplay was mostly abandoned by Riot themselves since the creation of Boards: with proper curating, more reliable developer input and a few changes to posting mechanics (removing the voting system here, for example, just like on GD, as it's abused more often than not), there'd be a much healthier overall atmosphere here, one that might even encourage Riot to post here more regularly and communicate more with their playerbase, but so far none of that has been implemented, in part because Riot's own philosophy of player communication (i.e. insisting on having developers talk directly to players, with no intermediaries) has prevented them from doing so.
The TL;DR to all this is that video game feedback forums aren't innately conducive to positivity, and in an environment where players essentially have to compete with each other for attention on the issue they care about (also upvotes, one of the many reasons why the voting system is broken), feedback just naturally devolves into hyperbole and shitposts, with little room for positivity. As much as the community here truly does need to change its attitude somewhat, that's not going to happen on its own, and Riot needs to put in work as well to improve the Gameplay board.
