People with social anxiety, or hearing issues raid all the time, people who are colorblind also raid all the time.
The level of social interaction required to do a raid is very minimal, you communicate through text with others to complete a task. No different than completing difficult quests back in the day that required more than just yourself. The problem is it takes a level of bravery to join a party/ raid group/static already. Then you have to take an even further step of bravery and actually use your voice to talk to people. Not everyone with anxiety is the same, not everyone with anxiety has it happen in the same way or at the same time.
It's really hard to say something as general as "typically people with high levels of social anxiety don't raid" without any proof ,statistics, or numbers to back it up, other than you "feel" that's the way it is based on your interactions. There are millions upon millions of gamers, and you think that everyone in the high end has no mental issues, high level of social anxiety, or problems with using voice chat?