The introvert/extroverts in social situations one is fascinating, particularly with people focusing on what they need/feel most comfortable with/prefer, without seeming to think about the other person or people with them and what they might need or like. To me, that’s selfish and rude.
I’m one who doesn’t find small talk or social situations terribly easy. I’ve had to work really, really hard at getting better at small talk because there were social situations I either wanted to be in or felt I should be in, or were requirements for my job. It still doesn’t come easily, but it’s easier with a lot of practising.
It is fairly awful, though, if you’re with someone at a social event - on a table with them at a dinner, say - and they make it clear they can’t be bothered to make an effort. Open questions are met with closed answers or monosyllables, and no effort at reciprocation.
If someone is clearly making an effort, or the conversation is flowing nicely without them, then that’s wonderful. If you’re at a table with one or more people who make it clear that because they don’t fancy making conversation they have no interest in whether anyone else is enjoying themselves - yes, that’s quite rude in a social situation. Because it’s selfish.