I'm in my mid-thirties and still recovering. Something I think is overlooked is that quite a lot of people are struggling to make friends as adults, not just those of us with AvPD or even social anxiety. I mean, just hang out in some of the larger reddits and you'll see posts asking how to make friends in adulthood. Almost all of the replies point to joining hobby groups.
Something I don't see mentioned much in those comments though, is that it takes time to make friends. It's hard for us because our brains are programed to find reasons we're being rejected. So when someone we like isn't moving at the same time-scale, we can get frustrated and/or feel rejected. It's just like therapy though, keep putting in the work. You won't see results with everyone, but definitely with a few.
I'm in a weird situation (in uni at my age lol) where I'm much older than the people/students who could be friends. I think I'm okay with them being acquaintances, because we all need those too, right? And professionally I will need to learn how to foster acquaintanceships anyway. But yeah, I still need that deeper "friendship" so I'm doing pickup games at a local game store, and joined a local gym too. It just takes time and work to build those