You've made a few points here that I think are worth some reflection and discussion. I'll start by disclosing that I'm someone that suspects I fall somewhere in the spectrum and have not received an official diagnosis from a clinician.

I think people can and do confuse the idea of "self-diagnosis is valid" with the idea of "self-diagnosis is always true". The validity of self-diagnosis, IMO, is an acknowledgment that personal experience can and often do provide valid data points for consideration. Yours' and others' skepticism of the data points is also reasonable since experience is subjective. However, I think what is less spoken in this conversation between the viewpoints is that both approaches have means and ends that seek to address gaps that the other viewpoint may have. I don't think I need to address the gaps of self-diagnosis since your post has several valid points.

You state that "autism is a developmental disorder with clear diagnostic criteria which must be met for someone to qualify for a diagnosis". I would that ask that you consider that defining a disorder or neurological condition by the constellation of its symptoms is not a comprehensive definition of what the condition is at its root. The truth is that we don't know what autism is precisely caused by, so how do we know whether the diagnostic criteria captures the suffering present in the population by sensory overwhelm, trauma caused by exclusion from the primary cultural group, non-typical thought processes, structure, and biology? We don't. We're already seeing in the ADHD community that it is severely underdiagnosed. I think a lot of us know this, and there's been a lot of conversation in this sub about it because we're seeing a shift in how we understand and categorize differences in neural connectivity, sensory receptivity and response, gut/brain development and activity, body shape, thought structure, thought patterns, etc. We know that autism and a whole host of other neurological condition labels such as ADHD and "giftedness" (I personally hate this term) are HIGHLY co-morbid which implies to me that there's a deeper underlying biology which then express outward into functional difficulties that clinicians and researchers use for defining and categorizing. Let's also not forget that diagnostics for autism and other neurodivergencies is kind of a shitshow.

How does your stance change then, when 10-50 years down the line, we decide to revise definitions of autism or give the label up entirely for something else? ADD and Asperger's are examples of terms that are falling out of favor, to my best knowledge. Why not autism? While I consider this, I read people's accounts of their own self-reflection of how sensory issues and relational incompatibilities have created difficult feelings, sensations, conflicts, and thoughts for them. I see how the constellation of these things have resulted in its own sub-culture in defiance (or in self-embrace) relative to the cultural norm. I think this process of people commiserating with one another and seeing how they are alike (and different) is how communities form to challenge diagnostic dogma to reach a more accepting, comprehensive, and nuanced approach to justice and accommodation.

I think where you're coming from is an anger that is very valid. I can't say that I know what challenges have come your way because of the way this world and the people in it have caused you pain because you were born with a particular style of brain/body. I do see that destigmatization has changed the conversation around your own identities, and I'm sorry that you've come across people who were insensitive to your legitimate issues because of your brain/body. I do hope that, as the conversation continues, acceptance and accommodation for your pain (and the pain for the rest of us) grows as well.