It's possible that people gravitate towards different drugs in a way that makes the users of any given drug a non-representative sample.

If I use myself as example. I don't use any psychedelics because I'm completely satisfied with my level of creativity. As a result it's possible that we completely lack data on how psychedelics mingle with naturally high creativity.

I also don't use weed, because it just simply makes me uncomfortable. That could be my brain protecting me from weed, as I may have strong tendency to go completely insane with prolonged use.

Those are just anecdotal speculations to illustrate a point. I'm not really claiming that they are any sort of facts.