Cold baryonic matter, MACHOs, primordial black holes etc were all candidates for dark matter at some point, yes they aren’t likely candidates at this point beca

Cold baryonic matter, MACHOs, primordial black holes etc were all candidates for dark matter at some point, yes they aren’t likely candidates at this point because we have much better telescopes and more complete surveys but the search for DM isn’t a process of elimination you can’t prove what is it by eliminating possible candidates you can only show where we might more likely to find a good candidate.