Though I agree that the term is used as an oversized umbrella - such is the case in many mental diagnoses - I think this is more because mental illness is such a a tricky, new and understudied field that most people just don't really know where to put things.

True autistic individuals are truly dysfunctional in every possible aspect.

This isn't true. Down's Syndrome kids with extreme autism, and other dysfunctional austistic folk can and have been nurtered to function in many aspects. In fact there are D Syndromers accepted into college and joining synchronised dance teams.

The accusation of bad parenting being the cause is a common one, and it seems you have the idea the wrong way round. For a long time, Doctors essentially accused parents of not nurturing their kids in the right way, and there was a certain shame and stigma against autistic kids.

Over time, knowledge developed and it's understood that this is no longer the case (As I said, I'm sure the umbrella is too big, but hear me out).

Autism doesn't just come with behavioural deficits. There are neurological and even systemic issues tied in, such as seizures, immune deficiencies, gastrointestinal disorders. We don't hear about this stuff because we typically only hear about the 'hyperactive' kids or the 'weird kids who dont look at you'.

Likewise, Language impairment is a real thing, as is extensive anxiety and other symptoms. Saying it's the parents fault is an easy way out but I don't think there's any proof to it.

Also, though the specifics are generally inconclusive, there is strong evidence to suggest it is genetic and indeed heritable.

Now I'm not only talking about the 'completely dysfunction, real' ones that are single digit percentages, but most of the strongly established forms of autism.

I think good parenting can possibly neutralise the effects of some weak forms, allowing a child to be nurtured into a fulfilling environment, and so a failure to compensate for their deficit could be a way to blame parents, but it's gonna be there regardless.

And finally, I agree that those defined on the edges of autism shouldn't be called a 'disorder' at all and we simply need to learn how to approach them differently, but giving them the diagnosis can be helpful regardless, if they are struggling to get through life for reasons beyond their control.

Diagnosing at birth is probably unlikely unless either paid for as a private clinic, or there are very strong concerning symptoms. I don't think most good doctors would be so quick to judge a child, otherwise we'd be in a pretty dystopian world right now.