Personally, I'd rather have a proper doctor prescribe me said medicine than take it myself.
The medical community is concerned with physical health, mental health, ect.
The Psychedelic community is more like a religion; it is "vast" and there is a lot of "shared knowledge" if you go looking. The thing is, western medicine's purpose really isn't to do the kind of thing that psychedelics are for.
It's probably better not to conflate the two communities, because they use drugs for very different purposes.
A different way to say it: Don't confuse the pharmacy and the liquor store.
That medical doctor doesn't even know how most of the medications work, or why!
If it was just about "health" a lot of things with our modern medical care would be different.
I think in most cases were the patient thinks he is smarter than the doctor, the latter already knows the argument, but also why it is wrong/more complicated. When something is understoodable by laymen, the doctor will be fine to understand it and better suited to judge it.
"How would they selecting medication, when they wouldn't know the mechanism of action?"
Mechanism of action is not known in 10-20% of current medications and treatments, across the board.
We /already/ prescribe things without knowing how they work.