> Galaxies seem to have gotten big impossibly early.
A MoND-like theory that allows the strength of gravity / inertia to vary over time can explain that. Granted, that sounds farfetched, but then, so does DM. Of course, it's easy to spend money looking for DM, and hard to spend money looking for a better theory of gravity.
Mond doesn't need that to explain early galaxies. When the matter is sparse gravitational contributions are weak and thus overwhelmingly in the O(1/r) regime and not the O(1/r^2) -- this makes gravity "seem stronger", and so stuff clumps together faster.
A MoND-like theory that allows the strength of gravity / inertia to vary over time can explain that. Granted, that sounds farfetched, but then, so does DM. Of course, it's easy to spend money looking for DM, and hard to spend money looking for a better theory of gravity.