> any serious civilizational benefit of drugs in the sub-hallucinatory regime is at least unproven

If you do want to get into the "where big":

Shamanic/ritual/religious/social practices that wholly involve hallucinatory experiences (both with and without the aid of hallucinogenic substances) are well attested and documented throughout human development.

So the existence is there; if you want to argue that actually it was a Bad Thing for human collectives, from Siberia to the Amazon, from 50k years ago to the present day, to engage in these practices and that they'd have been much better off Not Doing It, I guess the burden of that proof is on you?