No, it has never been this bad.
Then you haven't been paying attention. I remember the calls for Morello to be fired or lynched back in season 3. The name "nerfmaster sucktown" didn't come into play from a happy forum community. This place always, always, hates what Riot does. There has not been a time in its history when at least 80% of the content isn't extremely critical. That is the defining characteristic of the boards. Negativity in established patterns.
Hashinshin use to be a meme and now people are forced to agree with him.
Except when he complained about certain champions in season 3. Oh, and then the anti-tank bitching in season 5. That happened to. It's almost like Hashinshin comes into and out of popularity when the bitching he constantly does happens to hit a note.
There has been countless times where people tried to start bandwagons about a random champion and get shut down when their lack of content was exposed.
Yeah, because they went against the echo chamber that already existed. That's the entire point. If people ever try to be positive about certain champions, or negative about ones the boards have decided to like, they get downvoted. That's the way the echo chamber works. It's not negative about everything, and it is very defensive of other things. However, what those are does not vary much with time or game state.
The boards are filled with many different individuals with many different ideas.
Yes, and they get shouted down and downvoted if they aren't part of one of the circlejerks that already exists. The boards is strongly discouraging for anyone who doesn't agree with an established point of view from posting here.
The boards discourage people with different ideas from being part of the discussion. That's how the culture here works. If you aren't part of the majority, you're way more likely to be downvoted, directly insulted, and otherwise encouraged to not post again. It's worse about this than any other League community.
However, when all of the different individuals start coming to the same conclusion
This is where the problem with your explanation is. You're taking this as "everyone is coming to the same conclusion", when that's not what we're seeing. What we're seeing is a very, very vocal minority bitching about top lane, and silencing other dicussion. It's happened often before on the boards. This exact discussion happened late season 5 when top laners felt that they were underrepresnted at high level play. It's a very established circlejerk. The only difference now is that other communities outside of here actually agree, and there's actually something to it this time.
They are not happy when riot offers piss poor explanations.
Every explanation is piss-poor to the boards. Every single one. Even ones that the boards ended up being positive about after implementation were initially criticized. Even ones that inspired a lot of discussion and positivity in other communities were hated here. That's how this place works. Riot's actions are not viewed critically by the boards as a whole, because the most disparaging voices always win out when it comes to how this place views Riot's decision-making.
It makes sense too. They're the ones with some motivation to post. Why post if you happy with the game or the decision? Why downvote discussion if you don't feel annoyed or offended by Riot's decision?
You are buying into the memes too much and losing sight of reality.
You're not taking a critical enough eye towards the boards. You're falsely assuming that it is even slightly representative of the game's actual population. You need to step back, and really examine this place and its failings. It's not a failing of individuals, it's a failing of the community because of how this place is structured. That's not a meme. It's how this place has been, and it's the context that best explains the discussion here.