Oh, I don't doubt that sometimes something fundamental can be altered. The best sort of broad explanation I've seen that jives with the experience is maybe the one I've found here: https://www.frontiersin.org/journals/human-neuroscience/arti..., which I think would agree with your notion of a "reset" to fundamental neural structures. And yes, for certain conditions, like cluster headaches, as far as I know, psychedelics are the only things showing much real promise.

It can also just be easy for some proponents to forget that tonnes of people do and have done these things, with no clear significant lasting effects. And it is also common even for enthusiasts to say they they need to do take trips somewhat regularly (e.g. every few weeks or months) to regain the benefits. One-off miracles obviously happen, but I think are statistically likely the exception. And you can reverse or reject your insights, so for sure the trip is only one piece of the puzzle.

I'd love to see more serious research on psychedelics in general, to better engineer for useful and changing experiences. As it stands, just "take the psychedelic, manage your set and setting, and you'll have a significant positive effect" is generally not very plausible nor I think actually supported empirically or even by most anecdotes.