Let me start with the Melee-fanboys (who still thinks that Melee is superior to Ultimate).
The game is FULL of glitches, bugs and unfair characters (looking at you Fox).
And the competitive players are the worst. I can say that I'm a casual player that is pretty good at the game, and they're like "Oh ok but can you wobblesidestepdashjumpcancel? youre not as good as I am". Here's a hint: Nobody fucking cares about your SKILLZ in Melee.
Like ok, it's a good game, but no better than Smash 4 or Ultimate.
Then we have the people to HATE on Brawl.
I don't think it's that good either (except Subspace Emissary, holy fuck that was gold). I think the game is slow and unresponsive, and the random tripping sucks. But I'm not gonna talk down to people who likes the game, because it's their fucking opinion.
And lastly, the "nobody asked for that"-players who ALWAYS appears whenever a new character is revealed.
Like when Ridley and King K. Rool got revealed for the new Smash Ultimate, and the comments were flooded with "nobody asked for that, where is THIS and THIS character, oh another echo-fighter". Like shut the fuck up, Ridley and King Rool has been asked for since Melee.
TL;DR. Smash Players are some of the most toxic players on existence.