We have in fact detected one type of dark matter - neutrinos. They aren't sufficient to account for the mass needed to explain observations, but they are definitely dark matter in that they do not interact electromagnetically with regular matter.
The problem with modified gravity, is that it requires a lot more theoretical complexity to explain observations like the Bullet cluster and galaxy rotation, and the large-scale distribution of matter in the observable universe. Ie. a modified gravity theory that works for one of those observations, fails for others. Slow, massive dark matter clouds explain all of them quite nicely.
Neutrinos are made out of 6 prisms and they normally decay into 4 prisms. Those build up the grid structure of our vacuum.
another problem with MOND is, that it is in my opinion and a friend of mine that is more deeply into logic, not a classical logical explanation. We have no prove in a logical sense yet, but we both had the feeling that you need some more complex logic to get satisfy the max function in MOND. I asked my old logic professors, but did not get an answer...
The problem with modified gravity, is that it requires a lot more theoretical complexity to explain observations like the Bullet cluster and galaxy rotation, and the large-scale distribution of matter in the observable universe. Ie. a modified gravity theory that works for one of those observations, fails for others. Slow, massive dark matter clouds explain all of them quite nicely.