Yes, I think that you not doing something (because it is so emotionally draining/difficult/toxic) counts as "can't" for the purpose of this questionnaire. If you rarely do it, I would count it as severe.

I say this because for many people, dealing with people is no problem emotionally. Nor is making friends. In fact, many people like it. So your (and my for that matter) avoidance of these things is an extreme behavior.