If anything this just kinda suggests to me that the diagnostic categories are almost completely random/useless. It's just a set of pigeonholes made by people whose goal is to have a pigeonhole for every kind of thing so that the world doesn't seem messy and complicated anymore.

But the one thing we know for sure it's that the world is more complex than even this set of 10 pigeonholes. These are more like good insults for people. Haha, a loner, that guy's a schizo! The clinical coldness is almost a perfect mirror for the way we express personal cruelty to others. To reduce them to a factoid, an epithet. It's no wonder people want to reclaim these words as terms of identity, of pride, of nuanced meaning.

They are useful if they are understood properly. For example different "similar" groups respond to different treatments differently. Social phobia responds very well to exposure therapy, anti-social personality disorder does not. If you are able to follow the distinctions you are able to leverage more effective treatments. I don't think they have any use outside of psychological treatment though. This is a great video on a good way of breaking down how personality disorders in general are broken down and function and are separated. https://youtu.be/4mgifm3ftl8