It does taste very much like coffee (though it's also easy to tell it's not caffeinated) and placebo effect is real.

I have been experimenting with reducing/abstaining from coffee and I am well aware of its effects, and I doubt you can reach very strong conclusions. There are times where I have experienced no headaches during my abstinence week, others where I've felt terribly, this last one during the heatwave I actually felt pretty good staying away from coffee, and I have been enjoying the slower pace of my thought.

Nutritional research is, as always, as rigorous as astrology.

Personally, coffee makes me much more anxious, more impulsive, more able to bruteforce through things I hate, but reduces creativity and contemplation; just like amfetamine BTW.

Sure research rigor and reproducibility are known issues but if we're gonna complain about the study design it may as well actually take into account the study design. Seems like the biggest complaint W.R.T. study design is just the lack of a good control. Seems like it makes the case for something to do with gut health but then fails to definitively stomp out the placebo effect.