Labels are bound by many things. If you were alive with Autism in the past, the label would be as different as it will be in the future. Right now, regarding my "autism", I have had many. PDD-NOS, Autism NOS, and then, when I got Karyotyped, it changed to Chromosome 6 Aberration...Unknown Significance. Still have "Sensory Processing Disorder" on there.
Further, the same symptoms in people in different places or of different socio-economic means will get different diagnoses for the exact same symptoms. Researchers proved that in private hospitals people are more likely to get the dx of bioplar with psychotic features- in remission upon discharge while in public- schizophrenia diagnosis.
Further, a very smart PhD may give you a different label than a social worker fresh out of a bad university. Or maybe a Dr had a bad experience with someone who presents like you and he cannot get past it.
Even if we had blood tests for certain things, that would not help. Breast cancers are not considered one disease anymore. There are many different kinds. Same with blood cancers and brain tumours. Even an evident mass can be interpreted to mean different things. A friend was told he had cancer and went through chemo and never had cancer at all!
In the end, I don't think labels matter unless you either need them, are trying to escape one, know you do NOT have what they said you do , or KNOW that you have what they said you do not have.
I fear the horrors of the Nazi's and their labels of "Useless Eaters" etc. the most. I hope we are ALL beyond that. Those were terrible times for people with troubles.
So it's REALLY complication. I could go on and on about other nuances involved in both mental and bodily health issues........
I guess we need labels as a frame? What if we refused them? Could we function? A lot of people need a diagnosis for insurance, etc......
Oh, it is a HEADACHE being human!