I got diagnosed way later in life and by happenstance (a psychologist informally recommended me to check it, and later did so).

It was a big improvement in my life, both helping me understand why I am this way and cutting myself some slack.

While youtube videos and books helped, it truly was interacting with a professional that could see the whole thing from the outside, and giving me directions on how to improve certain things, embracing who I am and helping me fit in this world.

Like driving a truck in a sea of cars, do not expect others to empathize with your situation, but you can addapt and better understand yourself, hopefully meeting people with similar conditions.

Just a kind reminder: It's hard telling you've got a flat tire from inside the car.

The thing to remember, is that diagnosis official or otherwise does not excuse behavior

Do you mean it doesn't excuse being rude to people?

Yes in my experience, more people with self diagnoses seem to use it as an excuse for behaviour they dont seem willing to work on. I suspect the people I have in mind may even be a little more bibolar than autistic, and unpopular opinion: but those are also the people who are vehement that cannabis helps them cope even though a lot of those behaviours are common with cannabis dependecy.