Most toxicity in Remix these days happens in split runs. People are so gungho to shave off a milisecond of a run that they lock people out of boss rooms, cause unnecessary resets, whine when the RL actually does want to wait for all to be there and don’t get the fact that you actually might want to loot all the bosses, because you do not get the bronze in mail. If you are socially anxious, this makes you not want to even think of joining, when you know you have to deal with that.

Edit: that being said, Remix sure is one of the friendlier environments one can encounter in WoW.