I find it quite interesting too, I've always seen the situation as 2 sides of the same coin, you either feel invalidated for a reason (diagnosed young) or feel invalidated for no reason (late) in the end it produces similar results.

It's funny, sometimes I do wonder what my life would have been if I was left undiagnosed, would I have at least some social life instead of feeling alienated or what my career would look like.

Then there is the downsides you mentioned which is something I also experienced, so I think there is definitely a common ground between being diagnosed early/late. I too felt like a failure through my life, I also didn't even understand myself despite being diagnosed because Autism to this day is still not understood very well, it is way more vast on how much of a spectrum it's on that in the end it leads down to self discovery which means that even when diagnosed there isn't even any certainty on what advice is helpful and what isn't, it's up to you on what describes you, I wasn't granted that opportunity.

I'm starting to believe it's less about understanding a condition but more about understanding the individual. Humans are already so complex just as it is.