“Either the laws of gravity as currently understood are wrong, or there is something out there.”
Yes, but that “something” doesn’t necessarily have to be dark matter. Another force affecting the motion of galaxies in addition to gravity would be a much simpler solution than “smart matter” that somehow magically knew where it needed to be in every galaxy in order to make our equations work.
Neutrinos certainly exist, and they are “dim” matter, just barely detectable. It is not impossible that some other form of matter exists that only interacts with “ordinary” matter through gravity.
Despite your dismissive tone, dark matter seems to satisfy Occam’s razor as the most plausible explanation.