This post answers yours clearly: it is a spectrum.
> I think a reasonable definition would be a disorder
Homosexuality is not a disorder according to ICD or DSM. Autism is a development disorder. Schizophrenia is a psychotic disorder. Disorders cannot be cured, and cannot be treated either. One can learn to cope with them, but it cannot go away like a traditional disease. Its a verdict for life, so to say.
Someone with autism can have other issues, on top of their autism, e.g. ADHD or depression however autism is the main issue from which the other issues derive from.
The rest of your post is just denial, and I can only speculate why.
> The definition of mental illness should not slide so far as to begin to encompass people that clearly are not ill by any meaningful definition of the word.
That's why we have specialists who analyse people, and not laymen like people themselves, or people like you who claim about random strangers they "they don't have autism" or "don't have severe enough autism". Those people who get a diagnosis by said specialists who specialised in ASD generally don't get misdiagnosed. You may safely assume that those people have ASD. If they're not a child anymore, that generally means they have a relatively mild form but as you can read throughout this thread that doesn't mean they don't suffer, or that there's no room for QoL improvements. You can figure out how adults with so-called mild autism suffer by reading into their stories. The linked story is a great anecdote though unfortunately the subject didn't get a diagnosis.
I am lucky enough to live in a relatively rich country with decent healthcare. But many in our world, including in the USA, are not as good off as I am. Those people might run around un(der)diagnosed. That saddens me, as I've been misdiagnosed and un(de)rdiagnosed myself for a good 3,5 decades.
Homosexuality was considered a disorder by the DSM until 1973, which is what I was alluding to with my comment. And like most actions in psychology and psychiatry there was no scientific logic behind the decision to add it, or to remove it. It was simply proposed as a motion to the board of the American Psychiatry Association, and passed. Of course I'm not suggesting homosexuality is a disorder, but rather that their entire process of determining what is or is not a disorder has a very tenuous connection with science.
And this perhaps generalizes to these fields in general. The entire fields of psychology and psychiatry are currently in crisis in that their studies and research in general is now, more often than not, deeply flawed. I'm sure you aware of this [4] study which showed some 61% of major psychological studies published in reputable journals did not yield the results claimed when replicated. Follow up results from different researchers have corroborated this issue. One of the responses from the psychologists and psychiatrists involved in the unreproducible studies was to complain that they didn't use the nearly identical samples - for instance using students in e.g. Germany instead of students in New York. However that is a rather direct acknowledgement that these studies do not generalize in any way. But if they don't, then these fields are in no way producing science, let alone actionable science.
A very related issue here is the medicating of people. A recent study indicated that some 17% [1] of Americans are consuming psychiatric drugs. That number nearly doubled in a decade, yet the science on these drugs is very questionable. In recent trials upwards of 80% of SSRI's effects were explained by placebo alone. [2] That number should be doubly surprising as the side effects of SSRIs are, by contrast, very real and tend to undermine double blind studies. And the longterm effects are looking quite dire as well. This is all made more problematic by a pharmaceutical industry that sponsors research more aimed at them making money than on improving healthfulness of people. Emphasizing this is the fact that more than 50% [3] of preclinical medical trials also have results that were later found to be unreproducible.
This post answers yours clearly: it is a spectrum.
> I think a reasonable definition would be a disorder
Homosexuality is not a disorder according to ICD or DSM. Autism is a development disorder. Schizophrenia is a psychotic disorder. Disorders cannot be cured, and cannot be treated either. One can learn to cope with them, but it cannot go away like a traditional disease. Its a verdict for life, so to say.
Someone with autism can have other issues, on top of their autism, e.g. ADHD or depression however autism is the main issue from which the other issues derive from.
The rest of your post is just denial, and I can only speculate why.
> The definition of mental illness should not slide so far as to begin to encompass people that clearly are not ill by any meaningful definition of the word.
That's why we have specialists who analyse people, and not laymen like people themselves, or people like you who claim about random strangers they "they don't have autism" or "don't have severe enough autism". Those people who get a diagnosis by said specialists who specialised in ASD generally don't get misdiagnosed. You may safely assume that those people have ASD. If they're not a child anymore, that generally means they have a relatively mild form but as you can read throughout this thread that doesn't mean they don't suffer, or that there's no room for QoL improvements. You can figure out how adults with so-called mild autism suffer by reading into their stories. The linked story is a great anecdote though unfortunately the subject didn't get a diagnosis.
I am lucky enough to live in a relatively rich country with decent healthcare. But many in our world, including in the USA, are not as good off as I am. Those people might run around un(der)diagnosed. That saddens me, as I've been misdiagnosed and un(de)rdiagnosed myself for a good 3,5 decades.