I think autism is a term for a cluster of traits that have been identified by psychologists. Those traits exist on a spectrum of intensity. Many of those traits overlap with other words we have for personality types and behaviors, e.g. some autistic traits overlap with traits we might describe as “picky” or “meticulous” or “socially awkward” or “literal” or “argumentative” or many many other examples.
I think those traits exist. I don’t know what causes these traits any more than I know what causes any other traits. I’m not an expert on autism or psychology. I used to be very skeptical of people who claim that expertise. I still have some skepticism, but I’m not very interested in studying it in depth or arguing the issue. So I am a bit more cautious in expressing that skepticism with very strong/aggressive words.
But whatever the cause may be, the word is still potentially useful to describe that trait cluster. It means something. Maybe it means something medical or neurological. Maybe it means something memetic. Maybe both, I don’t know. Regardless, it means something in a descriptive social sense. The word means something, people can understand what that meaning is, and therefore it has descriptive value.
One reason people care a lot about differentiating biological vs. “learned” traits is that there is a common belief in society that it is easy to change non-biological traits and hard/impossible to change biological ones. I am skeptical of that claim. I think that skepticism is/has been common in CF and related communities. I think it can be hard to change behaviors regardless of where they come from, and many ideas/behaviors that are pretty hard to blame on biology are nonetheless hard for people to change. I suspect that humans are a pretty integrated mishmash of biology and ideas, and it is difficult to perfectly extract either element of that puzzle the way some people believe you can.
So I don’t really care much whether autism is biological or not. I don’t have a strong opinion on that, and I am not sure it matters much to me regardless.