Really interesting post...
I think it depends how you define "intelligence".
If you measure intelligence by IQ, I guess psychedelics don't do any effect on that.
But regarding knowledge about life and many other things... I think psychedelics can make a HUGE effect.
So many things you starting to see from new perspectives that you never seen or thought before.
I think I would just say that psychedelics can make you "smarter"!
But exactly like you said... "it CAN".
There a surely people that are not interested in learning deep shit. They take psychedelics just for party reasons. Maybe those can become more dumb then smarter after that. xD