But we are all interested in different stuff based on how our environment guide us.

That's an assertion that you haven't actually demonstrated and as far as my arguably limited awareness of research in the field goes, others haven't either. We know that we have different tastes and interests and we for sure know that our environment and experiences play a significant part in those, but there is not good evidence that the environment is the only factor. How do you rule out innate personality factors that might affect interests as well?

Let me point you to another post of yours about cats and their personality. There you seem to point out behavior traits that are innate, right? I'm sure you agree that there are some behavior traits in humans that are innate, too, right? Well, why would you rule out the possiblity of a personality trait being optional? Why wouldn't it be possible some people to have an innately different way to process external stimulus. Of course, I'm far from proving this, but I think it's an option that is unreasonable to dismiss yet and it seems to me that it fits well with the evidence we have about autism and especially the more severe forms as I too am not entirely sure we are drawing the line fuzzy as it is at the right place.

Your example is merely a simple behavioral pattern that we could be caused from a myriad of factors — especially early development ones.

Possibly, of course. But that hasn't been actually demonstrated to be the case. That's why I'm saying that it's way too early to rule out the innate option and I personally find it to have a bit more merit as of now. And it certainly doesn't have to be an either-or thing anyway. We could easily have all kinds of people that are currently on the spectrum with very different reasons for a similar condition. What I don't understand is why you discount all the other options in favor of one and that's why I'm discussing this.

the meme is the over-diagnosis. the "spectrum" includes literally everyone. Where does on draw the line between "normal" and not?

We agree about over-diagnosis entirely I think.

Drawing the line might be a challenge and the middle ground might contain a lot of fuzziness, but I think it's already clear that people on either ends of the spectrum function very differently from a practical perspective. That's why I think making a differentiation does make sense despite the fact that I'm not sure that either ends of the spectrum are warranted to be viewed as disorders. That's why I think having it is not pointless, we should just not allow for the "diagnosis" part to eat up the middle ground.