For example, I expect that sociology has a lot to say about many of our cultural assumptions. It is quite possible that 95% of it is either obvious or junk, but almost all fields have that 5% within them that could be valuable.

While I agree, doesn't it take already possessing a measure of rationality, or something, to pick out the valuable 5% of a field from between the pile of 95% junk. Sociology is presently as popular as it is because enough people thought it was a field that was valuable. They thought a lot of the 95% wasn't junk, even though it still was. What would we do different to do a better job extracting value? There are two failure modes:

1. either we end up believing junk has value.
2. or, we end up throwing the valuable in with the junk, passing it over, and being no better off.