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.