I mean, that's the nature of empirical sciences. You establish a model that fits observations you've made, but inevitably their is some chaotic, sometimes imperceptible noise that gets averaged out that represents some further level of complexity.

I wouldn't argue that it means we don't know much, in the end you can argue we don't know anything because all empirical sciences are beholden to the belief of abstractions that can be attributed to some imperceptible abstraction until you (don't) reach the bottom of the stack of turtles.