> A problem with modern psychology is the diagnostic criteria aren't very much based on underlying causes as on being able to reliably diagnose patients based on symptoms regardless of physician. This leads to people agreeing what your diagnosis is

That is true. The groupings persist because they are useful in facilitating communication regarding potential complications, prognosis, and patterns of response to treatments.

People seem intent on throwing away the above utility with a backhanded “but that’s not the Real Diagnosis.” It’s not, but within the limitations of our current understanding of neurology, it’s the best we have come up with so far (allowing for some limitations due to the pace of spread of innovations, politicking, etc.)