The real distinction here is mechanism of action. Psilocybin helps fix psychoemotional problems in an enduring sense. You take one, or three, doses and your personality and self-understanding are permanently altered.

Alcohol works acutely. So I totally agree the term therapeutic is an arbitrary label; all drugs have effects and thus can be therapeutic for condition X and deleterious for condition Y. But worth noting that psilocybin and MDMA produce enduring benefits whereas alcohol appears not to.