I think primordial black holes are the Occam's Razor solution too. No exotic new particles required, no modifications to gravity required, no new physics period. Observational results have ruled out certain masses of black holes but far from all.
Primordial black holes do not require new fundamental physics, but for them to constitute the primary component of dark matter would require a revision, at some level, of our narrative of the history of the universe. This gets a bit outside of my core knowledge, but as it stands there aren't any super solid mechanisms for generating black holes of a plausible mass distribution, early in the universe, such that we would see what we see today.
But, IMO, this is worthy of more study both theoretically and experimentally. An update to the evolution of the universe would be awesome!
