But, until we figure out why galactic rotation curves are wonky, everyone will claim everything is due to dark matter.
Well, rotation curves, gravitational lensing by galaxies, missing amounts of matter needed in the beginning universe to show us what we are seeing today, and about four other separate methods of observations that are all hinting at the same thing. Thing is that this isn't a fad, it's been one of many different theories put forth and tested since these observations started popping up in the early part of the 20th century. So far, everything theory that hasn't been "matter that doesn't interact with EM radiation" has failed while "dark matter" actually has successes such as the Bullet Cluster. Meanwhile, such explainations such as MOND, modified gravitational equations, have yet to come up with even a hypothetical example that matches what we see. It's not a fad at this point, just tested science. Difference is that you are just hearing about it. It is a developing theory, less than a hundred years old from the first observational evidence, but at this point, if what is causing all of these observations isn't "matter that doesn't interact with EM radiation", it's something that acts just like it and is much stranger.