But for psychodynamic and trauma therapy it may NOT be relevant. Especially, if after working very hard for many years in "regular" therapy, one eventually gets a diagnosis of a dissociative disorder.

Earlier, non-specialist therapists did not diagnose -- may not have recognized -- the dissociative disorder. Some people may not understand or do not recognize or accept the validity or reality of a dissociative disorder. In that case it may seem to them that the person is not doing their part in therapy when, consciously, with everything they have with the most adaptive part of their personality, they may be.

Even in CBT, which I have never done although I have done other therapies with homework and had no problem doing the homework, if a person lacks the motivation to do the homework -- that seems more to me like something going on in the motivational system of the client that neither the therapy nor their existing coping skills are addressing. But the existing coping skills are what the client has, what they come to therapy with. Something which they are looking to a "therapy" to help with. If the therapy doesn't, then it's the therapy's failure, for that particular client, in my view.