True beliefs are pretty darn useful, so epistemic rationality contributes pretty strongly to instrumental rationality (i.e. the one that matters by definition).
Interestingly, as I've become more aware of what I want out of life and see more long term challenges, epistemic rationality has begun to seem less terminally important - yet still very instrumentally important. It's just that the purpose of epistemic rationality is much more gut level clear to me now - the reason to have a really good map is to get places, not just to hang up it up on your wall and admire for its accuracy.
Additionally, I've become much less hung up on "literal truth" (that is, truth as straightforwardly explicitly/denotationally interpreted) since I realized that that's not really how people work - so obsessing on that level is a bit silly. Once you really grok the idea that true beliefs are for navigation, then you can use all sorts of funky encodings - as long as you keep track of them. If you take a bunch of magic mushrooms and the world starts bending, it's not a simple map, but the information is still mostly there - and you don't run into problems until you forget to walk the same bendy that the sidewalk bends. Try to walk straight and you're in for trouble. And phrases like the "most amazing show ever!" are totally acceptable too - as long as you realize that it really means "I'm experiencing awe and very much enjoyed the show".
Putting these together can explain a lot of "irrationalities" people have where they say stuff that is just blatantly not true and don't seem to care when you point it out.