It's not even scientific. Quantum mechanics seems to be how our world works and the only realist versions of it are very exotic, like predicting an infinite multiverse.

Yes. Sticking only to the realm of hard science, the frontiers keep expanding (e.g. dark matter and energy). When it comes to our subjective perceptions and how the the brain assembles them into consciousness, we've barely a clue.

Scientific apparatuses have allowed us to "see" the complete elecromagnetic spectrum, the cell, the quasar... psychedelics may be an apparatus allowing us to see dimensions of reality heretofore unquantified.

There are frequencies we can't hear -- impossible with the physical equipment nature has provided in our ears. But science and engineering have a means for both proving to us they really exist, and mangling them (with a kind of fidelity) into some sort of analogous experience. Similarly there are frequencies in the electromagnetic spectrum we cannot see. And microscopes, and telescopes and MRI's, and all the other wonders of our day take, which take a world that is impossible for use to sense directly and transform it into an analog we can sense.

So why do we cavalierly assume that our brains are physically capable of understanding all true things? What does a machine which transforms ideas which are literally inconceivable to our physical brains look like? What do the crude analogs of these inconceivable thoughts look like?

(I realize I've drifted far afield from the OP -- I don't mean to say that psychedelics are a window into true mysteries. But these discussions always seem to lead me down this path...)