I think the whole fast vs slow thinking is also a bit tied up with kind of like "raw intelligence" vs "trained skill". I think there are some people who are really really smart and fast thinkers, and some people who are less smart and slower. But the thing is, being smart doesn't mean being right. Especially as things get complicated where methodology or background research become critical components of getting the right answers. Knowledge is probably more important than intelligence in the application of knowledge. Intelligence may be more important in the discovery of knowledge, and even then, it require the sufficient patience to acquire prerequisite knowledge in the first place.

I'm not sure that one is better than the other, but I suspect there is a lot of frustration embedded in mismatching what you want to be doing vs what you are good at.