Think of the universe as a painting. There’s the image made in paint, and the surface it was painted on. The canvas.
The stars, the planets, the gasses, the matter and energy and even the space between are the paint. What’s the canvas? Is there a canvas? Would the canvas follow the same rules as the paint?
In the first picture, the object in orbit is travelling along, say, y=0. There could also be an object in orbit along x=0, right? So that would mean there isn’t a “canvas” or 2D equivalent, since things can orbit at any angle. Is that right?