I've tried my best not to frontally engage any of the internal techniques or justifications of rationality. On what Robin Hanson would call an inside view, rationality looks very, very attractive, even to me. By design, I have not argued here that, e.g., it is difficult to revive a frozen human brain, or that the FDA is the best judge of which drugs are safe.

To be honest, I think you should have. Meta-arguments for why the causes of our beliefs are suspect are never going to be as convincing as evidence for why the beliefs themselves are wrong.

Also, I think the parts about psychoactive drugs are somewhere between off-topic and a straw man. One of the posts you linked is titled "Coffee: When it helps, when it hurts"--two sides of an argument for a stimulant that probably a supermajority of adults use regularly. In another, 2 of the 18 suggestions offered involve substance use.

Thirdly, while rationality in the presence of akrasia does not have amazing effects on making us more effective, rationality does have one advantage that's been overlooked a lot lately: it results in true beliefs. Some people, myself included, value this for its own sake, and it is a real benefit.