Transcription: crude line drawing of a young goofy person sitting in a school chair. They have mid-length straight red hair, messy and needing a trim. They are wearing a hoodie of GIR from the cartoon show Invader Zim. That character is a pet-coded green alien dog with a goofy long tongue. Dialogue: off screen character saying "She has Aspergers" main character thinking: "ha ha ha ass burger" Thought bubble of a very crudely drawn pair of butt cheeks and a hamburger. End transcription.
Nuance is needed here... The terms high- and low-functioning are definitely problematic, because they're too reductionist, and lead people to assume things. But I wouldn't go so far as to say that autism having "levels" is bad - the DSM-5 (as horribly flawed as it is) contains two sets of three levels each for determining level of support needed by an autistic person, with the two sets being related to socialization and life-skill functioning. Given that autism is a spectrum, and some autistic people aren't disabled by it at all, being able to categorize people by their needs is useful - we just have to make sure that it's qualitative, rather than arbitrary labels being picked by how the doctor is feeling that day. And it's something to be kept in medical records, not used for self-identification.
I understand this thought process, but us in the schizophrenia community are very familiar with this change. Schizophrenia went from having 3-5 categories based on symptoms to just being the umbrella term for everything. The names for schizophrenia categories aren't particularly negative, but because it's more of a spectrum, categorization of people lead to worse treatment. It locks down an idea of how those symptoms should be treated, and that's the issue.
I'm not sure that the labels themselves are the issue in either of these cases. It's worth remembering that we're talking about historical periods of mistreatment as well. From my experience, Psychiatry as a whole has historically had its favorite diagnosis for the 'bad and unwanted' people in society. Hysteria is the obvious reference, but that shifted towards labeling the 'undesirables' as schizophrenics (and later as borderlines). It wasn't (and in the case of BPD, still isn't) uncommon for people to receive these labels purely to communicate to other doctors "I don't like this patient"/"They're faking"/"They deserve mistreatment".
Let's not forget that the label of schizophrenia started as a combination of the idea of early-onset dementia and stigmatization of behaviors that do not fit into society. The latter half is covered up by history, but the initial 'symptoms' of a schizophrenia diagnosis included things like not making small talk and having strong beliefs about politics. The list of symptoms read half of what you'd expect in terms of psychosis, and half like it was copy-pasted from the 'symptoms' of Hysteria. That's why these additional labels were harmful - some of them were associated more with not fitting into society than actual pathology.
It's no coincidence that when this general issue of mistreatment and over-diagnosis was being fought against, Psychiatry was busy switching over to using Borderline as the new maligned diagnosis. The schizophrenia labels were removed during the wider push for humanizing treatment of schizophrenics, but I don't think the labels themselves were a significant part of the issue - the bigger issue was the inherent power imbalances and patient abuse present within Psychiatry. After all, BPD was previously unnoteworthy, but now has become the new stigmatizing label, and all the mistreatments of schizophrenics are being shifted to borderlines. After all, there's now a "quiet borderline" label - for people who clearly aren't borderline, but psychiatrists want to give the 'bad diagnosis' to anyway.
Autism is adjacent to Psychiatry, but the story is the same. Autism is currently maligned by society, and the fact that people are so hostile towards autistic people is the real problem, not the labels they've made up to 'justify' their hostility. Getting rid of the labels doesn't remove the hostility, because the hostility is just looking for an outlet. That's why my only focus is making sure that labels are medically useful - because managing societal and medicalized hate of disabled people is another issue altogether.