>> I thought that was actually true. Why are you calling it tired and old?

Because there is no reason to expect stars going around a galaxy to follow keplers laws for two body systems. I have yet to see the measured rotation curves compared to an "expected" curve where the author doesn't use Kepler as part of the expectation.

Just a year or two ago, I saw a paper in Nature where they were looking at a gas cloud forming a star, and they compared its rotation to something based on Kepler. I just had to shake my head - the correlation was there but not a great fit of course. The curve is interesting, the comparison not so much.