I agree with your first sentence. But not the rest of your post.
Most of these diagnoses are very real, and they can help a person make sense of their lives, when they had previously been drowning in confusion and misunderstandings.
I personally had 50 years of not even knowing that I am Autistic (the explanation as to why that happened is a long story, but it does make sense) and once I've started coming to terms with it, I'm pretty much coming into my own at long last. It's been such a long journey and at least it has taught me many things that I needed to be taught, even if it was the hard way, in order to get them into my Autistic head.
I do also struggle and take a lot longer to learn and understand some of the more subtle, flexible, complicated, and nuanced social skills that real life interactions entail. Reading fiction seems to help clue me up a bit more.. Even a popular commercial author like Stephen KIng is fantastic on what he has to say about human psychology and interactions in his books. Many other writers too, probably greater writers too, but when you need to do a degree to understand wtf they are on about I think that is a bit much.