One counter theory (oops, “hypothesis”) is that the “missing matter” is actually the stored gravitational energy of systems “weaving” among themselves (my wording.) kind of like how intense magnetic fields “braid”, in a galaxy scale all mass bodies are not sitting evenly dispersed on the orbital plane (by accretion,) rather they are perturbing each other in complex orbits as the disc churns, storing more gravitational potential than may be visibly accounted. Like a spring (compressing a spring actually increases mass.)

Galaxies without these complex orbital currents would correlate more consistent visible mass estimations.