Here it is, basically:
Stop trying to create a manual that works for both psychotherapy and for psychiatry.
Here's the thing: The wants of psychotherapists and of psychiatrists are different. Broadly speaking, psychiatrists want to know what the mechanisms are behind disorders so they can more accurately provide chemical interventions. Whereas psychotherapists want to know what clusters of symptoms respond to what interventions. Psychiatrists want to know how to provide the most effective chemical for a given clinical presentation. Psychotherapists want to know what techniques to use with someone who is reporting symptoms like crying spells or panic attacks.
Many of the critical voices from the psychiatric community want mental health to have more of a biological basis. These folks want to understand the biology of mental disorder--they want to move away from classifying symptoms, and towards classifying underlying biology.
But the criticisms of the DSM-5 from the psychotherapy community are often focused on the increased medicalization of normal life experiences. In other words, the psychotherapy community and the psychiatry community have opposing desires. One side wants to reduce mental health to biology of the brain, the other side wants to see mental health as a holistic part of human life.
Further, clients who present with adjustment issues, or grief, or any of the other countless parts of a normal life that cause someone to want to see a therapist, do not need to be shoe-horned into a diagnosis that they do not fit. And, we can treat these normal life issues as just that--normal life issues--that are not pathology.
The reality is that it might be impossible to create a manual that identifies disorders based on biology and also on symptoms. And maybe it is in our best interest to stop trying.