Why are casual players always hated?

I don't care about competitive. I don't know what's meta, I even read the patch notes and forget all the changes in my third game. My friends think that I am not a "true BS player" because I seldom play ranked (only when my friends want to) I just want to play and chill

Why is the brawl community so focused on being good at this game? If I pick an off-meta character (I don't even know what's the meta anyway). My teammates begin to flame me even if I perform well in-game.

I just want to have fun in casual. Nothing happens if my team wins/loses that's only the end of the game, all I care about is playing not the result. Why does everyone think that every game is a Worlds Final? It's so frustating.