No, observations of galaxies that seem to have little dark matter are an argument for the existence of dark matter (over the competing theory of a modified grav

No, observations of galaxies that seem to have little dark matter are an argument for the existence of dark matter (over the competing theory of a modified gravitational interaction). And here is why: If you have two galaxies with about the same size and about the same number of observed stars they should have about the same distribution of barionic matter. So gravity should work the same in them, no matter if that gravity is described by Newtonian theory (probably not), General Relativity (I would assume that, but who knows) or your modified theory of gravity (maybe, maybe not). Any difference between them can not be due to the theory of gravity. But it can easily come from different amounts of un-seen dark matter.