I think, like, 80% of individuals with classic autism are ret*d? Like if someone has Aspergers and is gifted I can see them being mistaken for a brainy introvert, but even among the Aspergers population there are plenty who are of average intelligence.
I'm not sure how to articulate what I'm saying here, I mean, you can be 'high functioning' and have a lot of autism-related issues. But when people talk about autism not being a disability, they're often talking about the people who are eccentric but manage to go to uni, be a part of society, and they're the minority of autistic people. But to replace the word 'autism' with 'introversion' would be grossly inaccurate, despite there being overlap between the concepts. Maybe you should go out and meet some people with autism, because this forum is not representative of the autistic population.