That not them being terrible thou.
That is them using there right.
No one has to play with you.
Making them play with you is what would be toxic not even lfg did that. As lfg allowed them to freely kick you with a vote and in wrath there wasent even a cooldown on it.
You having social anxiety is your problem not the problem of random people you see in game. They have the right to pick to play with you as much as you do to pick to play with them. If they don’t want to play with you that’s not being rude at all that is them enjoying there own game. It’s your issue to deal with them not wanting to play with you by finding those that do. The only thing toxic here is thinking people have to play with you ie you having a issue with them removing you.
It is not bad behaviour to remove a player you don’t want to play with its in fact what blizzard outright tells them to do.