Placebos also have known physiological effects on the brain and there are clear differences when taking a pink placebo vs a blue one: https://www.thelancet.com/journals/lancet/article/PIIS0140-6...

This is not to downplay the effects of psychadelics - I've taken plenty and of course the psychoactive effects are undeniable. But the effects are from far more than just the chemicals. For example smoked DMT hallucinations are very different than Ayahuasca, despite the two being the same chemical.

Hmm, I see what you are saying. I'd like to see a comparison between the effects of established placebos on the brain versus psilocybin. My hunch is that the mechanisms are quite different, but maybe there are some interesting similarities.