A good point. I have heard of primordial black holes as a candidate for (at least some) dark matter. Not heard that dust was ever a candidate (if you have a reference it would be appreciated).
Baryonic (tangible) dark matter exists in the form of MACHOs, which includes small cold planetary-mass dwarf stars. But there's a limited number of these, and the Big Bang hydrogen helium ratio puts limits on the amount of baryonic matter there can be.
I think there are too many unknowns and we are nowhere near close to fully understanding our universe that we should be open minded to new ideas and see if they fit into our understanding. Dark matter is one explanation to the bullet cluster but perhaps there is another we just don't understand. Yes if someone has a perpetual motion machine to the spam folder but I am always open to hear new ideas to our universe.