Guess what that leaves us with to explain the orbit of the planets around the Sun?!General relativity works the same (i.e., it gives a consistent result) in all frames of reference. You are the one saying that coordinate system matters. Why would you expect the orbit to remain stable in the "motionless" coordinate system, but not in a moving coordinate system?
"General relativity works the same (i.e., it gives a consistent result) in all frames of reference."
As will the answer to our questions on this thread.
Are the Earth and Sun stationary?
Well, that's not consistent in all frames of reference, so that's probably not our answer.
Could Gravity be moving really, really fast to explain why the Earth appears to be orbiting in a plane around the center of our Sun?
Well, that *IS* consistent with what we see in all frames of reference. Hmmm...