I am diagnosed bipolar and ADHD, but meh I don't really care that much about labels.
What helped me become stable and happy is going to a therapist. What helped me succeed in the workplace is reading books and applying what I learned.
> Burying your head in books and overanalyzing your social interactions isn't going to solve your social anxiety. Go play soccer.
Not everyone is able to play soccer, or naturally athletic. And honestly it comes off as very "pull yourself up by your bootstraps, bro." So fine. You hate therapists and cured yourself. Congratulations. I'm just saying what works for me.
HOWEVER, I strongly agree with your assertion that "introverts" tend to be stuck in their ways. Branching out and trying new activities, joining clubs, and being physically fit are extremely important to a person's mental health. Having more interests other than video games, anime, and internet culture goes a LONG WAY in having better social interactions with people.