It's human nature, people get themselves into ruts or patterns. They get used to playing the game "by the book" aka following the meta. They build up expectations about how the game is "normally" played and that it "should" be played that way.
They also expect a lot of everyone else without ever communicating that to them. People get caught up in the game and in their own selfish desires. Some people care way too much about winning, while others care way too little about winning and instead care only about having fun.
There is no right or wrong position on the spectrum between fun and trying-to-win, what is wrong is when people assume other players are like them, and then get pissed off and feel betrayed when they discover that this random stranger that they never tried to coordinate or communicate or build trust with has suddenly violated their expectations.
And it goes both ways, it's really upsetting for a tryhard to discover that their teammate feels okay with playing something they don't know how to play well "just because it seems fun to them." And it's really upsetting for a fun-seeker to discover that their teammate thinks "it's okay to tell them how to play."