I think its relatively easy to make it beneficial with an adult person taken in most serene settings & with good intentions. The studies they did do seem to reflect that.

I would advice against a too high of a dose first time. The 5 grams they normally give in studies seems to be on the high side for a first time.

Set and setting can help make a positive experience likely, yes, I think what proponents often miss is that for the vast majority of people, the experience will mostly just be "interesting" and "memorable", and not particularly transformative. I.e. transformative / curative effects seem to be rare, IMO for the reasons I already stated.