Pollan actually does go on the black market (still probably $200/hour though). You can't legally get a psychedelic trip guide in the US right now.
The point is that the exact people who are well-known and respected as black-market guides would become therapists in a world where such a profession were legal!
Consider expanding your definition of what a "therapist" could be and what a "clinical setting" could look like. Michael Pollan's interactions with the therapists (they're called "guides") in "How to Change Your Mind" are not clinical at all in the sense of sterility, beige-walled offices etc.
It isn't hard to give an AI a goal but it is hard to do so safely. As a toy example we could design an AI who treated say, reducing carbon emissions as it's goal just as you treat eating and sleeping as yours. The issue is that the sub goals to accomplish that top-level goal might contain things we didn't account for, say destroying carbon-emitting technology and/or the people that use it.