I was looking at the question from a much less optimistic angle. Sturgeon's Law was originally a defense of science fiction against people who'd mock the worst of the field as though it was the whole story. (Science fiction used to be much less respectable than it is now.)

However, works of art are separable from each other. Intellectual disciplines are much more entangled.

If psychology is proposed as a tool for improving philosophy but a great deal of psychology is fascinating nonsense, your percentages look worse. There's a risk that psychology will damage philosophy rather than improving it.

Also, eliminating abject failure isn't the same thing as making the remainder useful.