Isn't gut health just about having more good bacteria and fewer bad ones?

It is a natural way to think about it, but the science has moved past that framing. Very few gut organisms are simply good or bad. What matters is the community as a whole – how diverse it is, what it is collectively able to do, and the environment it is living in. The significance of any single species depends on what else is present around it. That is why a test that returns a list of organisms, on its own, gives you data without much of the context needed to make sense of it.