> This sounds crazy but they should really be looking back to the roles/practices of priests, even shamans, just to try and get some semblance of an idea of what works and what doesn't
These things are exactly what psychoanalysis did and has always done. That kind of historical and reflexive investigation appears in plenty of Freud's writings (as well as later theorists, like Lacan, who drew heavily on Levi-Strauss's anthropological work).
Too bad that psychoanalysis takes shit for being "unverifiable" and "unfalsifiable" (as if what we currently have doesn't suffer from the exact same flaws, which I believe are inherent to any study of mental phenomena).