[isthatafact]

There is no DNA for galaxies, so how could you know what the properties of a particular galaxy "should be"?

The focus on "per-galaxy parameters" is like expecting to be able to predict how tall Tom Cruise should be after reading a textbook on the theory of evolution.

[throwawaymaths]

Ok so you are admitting that just as evolution is a poor model for human height, DM is a poor model for galaxy rotation curves.

[isthatafact]

Maybe my metaphor was too sloppy to illustrate the point, but I do not follow your logic here at all.