There are theories that work without resorting to “dark matter” pixie dust, but the physicists and cosmologists just prefer their existing theories, because they still hold out hope they can prop them up if they find the “dark matter”.
...
Maybe all those physicists and cosmologists simply aren’t as smart and knowledgeable on the subject as you are.
No, I don’t think so. If you look at the history of science, much of it is filled with very intelligent men holding on to flawed theories that should have been abandoned, in the name of scientific orthodoxy.