Welcome to the forum. I haven't really been in a relationship either. I've never worked. I can't drive. I doubt I'll have kids. I do my shopping online. A lot of this is for health reasons, but I can't say I'm disappointed that I get to avoid these challenging situations. I'm seen as an introvert and that's probably true, but being an introvert doesn't necessarily mean you don't want to be around people at all. It just means we need less interaction than other people - and not all introverts are the same (and not all extroverts are the same) so we don't all need exactly the same amount of interaction. But because negotiating life as an introvert can be difficult, we often end up with less interaction than we need.
But I think the main problem here is, as you say, anxiety. We live in a world where we are ridiculed and ostracised for being different. Some of us will have experienced that already. School can be a minefield. So can family life. We naturally don't want that to be ridiculed or ostracised and when we feel within ourselves that we are different, that can make a lot of things scary. Every interaction is a possibility for us to be exposed, ridiculed and ostracised. So of course we want to avoid situations that make us feel like that.
(When I say 'we', it's a very general sort of 'we', I'm not speaking for you. It just feels right to say 'we' than to say 'I' all the time when it's not about me.)
But it can get very lonely and sometimes we do something different and that's natural.
Exactly how you deal with the problem depends on what you want - I don't want to make assumptions. Would you like to be doing some of the things you currently aren't able to do? Would you like a trip to the grocery store to be an option if you need something urgently, even if it isn't your first choice? Would you like ways of dealing with the emotions you're currently experiencing? Or do you just want to chat to people who have similar feelings?
Sorry for all the questions and obviously, there's no pressure to answer any of them, but I don't want to give you ideas about a trip to the grocery store, for example, if that doesn't interest you or isn't your main priority.