I agree with you that outright claims of "therapy doesn't work" should be backed by evidence.

But a patient feeling better at the end of a single therapy session doesn't prove that therapy works either...

- Does the patient feel better between sessions too? Will they keep feeling better after the therapy ends? Aka are they "cured"?

- Would the patient feel equally good if they confided in a non-licensed therapist?

- Do the techniques (CBT, DBT, ACT, IFS, etc) actually provide tangible benefits versus just listening and providing advice?