Some of us have exceptionally good theory of mind.
Ironically, sometimes due to having grown up with undiagnosed autistic parents who made us suffer if we didn't constantly dance attendance on them. But also due to being expected to understand allistic people the whole time without any explanations, while a lot of them experience no pressure - let alone an equal amount - to understand us.
I've been lurking on this thread a bit because of my abuse by other autistic people, and ordinarily would add a bit to show that - due to those experiences - I do know where people are coming from on this. I don't have time right now. But I can't let that one pass.
Poor theory of mind is yet another thing that anyone can have, with a higher incidence amongst autistic people than in the general population, sure, but it's not what autism is.
It's not selfish to point that out, given that some people who've struggled with the specific autistic traits possessed by those around them are themselves autistic. Not everyone who's suffered due to someone else's lack of diagnosis/support/self-awareness is allistic.
The conclusion I've come to in the end is that someone being not right for you due to a disability is no different to them not being right for you for any other reason. I don't understand why there's this idea around that it is. Maybe it's lack of awareness/visibility of the range of disabilities that exist; something that affects someone's personality is going to be different, relationship-wise, to something that affects their mobility, for example.
But it's clear that it's drawing in, and causing a lot of suffering to, vulnerable people, both autistic and allistic. It's ok to leave someone - or turn them down - because of something they can't help. Or because they've changed, long-term, into someone who takes more from you than they give back.