Everything may be explainable, just not by humanity.

How does our biology affect the limits of what we can comprehend?

Oh plenty of ways probably. I expect there are perspectives out there which would have a look at our biggest questions and find them to be mundane with obvious answers but which would themselves boggle at concepts that we consider elementary.

But here I am in this body, and not that one, so I'm content to accept an axiom or two.

Gravity is something very simple. It cannot be a complex thing, because it demonstrates a very simple behavior.

There are plenty of cases where a complex thing has very simple behavior. For centuries, brewers could get away with a mental model for yeast as something that multiplies and converts sugar to alcohol until it can't anymore. It took quite a jump in technology to realize just how fantastically complex the inner workings of a yeast cell is.

I'm not proposing that gravity is underpinned by something complex, just that if its mechanism is out of our reach then so to are any conclusions about that mechanism's complexity.

the question is depth and quality of explainability as determined by the predictive power those explanations provide...