Funny you mention placebo effect. It actually is probably far less of a thing than popularly believed see https://slatestarcodex.com/2018/01/31/powerless-placebos/

From one point of view that just proves your point more, from another, less. If placebo effect is tenuous then all else equal that’s a good sign for the rest of medicine… but in fact lots of medicine is tenuous. The landmark “Most Published Research Findings Are False” was looking at medical findings iirc.