> We actually already know GR must be wrong because of its singularities

This is not why we "know" GR must be wrong.

You keep making very strong assertions that any expert -- including those not hostile to MOND, or even positively in favour of properly capturing the empirical MOND relation into some other theory (whether that's the standard one or one like Bekenstein's) -- simply would not make.

I do not know what you are trying to do here on HN, but it does not seem to be an attempt to honestly help people who are interested in dark matter but who lack expertise; it doesn't seem to be an attempt to acquire expertise you clearly lack; and it doesn't seem to be an attempt to work out how you yourself might better understand difficult concepts through a process of ELI5/ELI12. It seems, frankly, like you just enjoy being rude on hackernews.

In order to make up for the observations above that might be fairly taken as leading off with insults, I'll supply some related real, standard, uncontroversial physics discussion.

The principal problem with General Relativity is that the stress-energy tensor when generated by real matter (which we know can behave quantum mechanically) must in principle be able to encode superpositions of (at least) spin, momentum, and position. However, the Einstein Field Equations are fully classical, so how to do this encoding is not known. As a result "hacks" like taking the expectation value of the stress-energy T_{\mu\nu} -> <T_{\mu\nu}> are used to make the EFEs work at all. Unfortunately this averaging generally destroys superpositions, so one runs into problems like: if we took a fairly large molecule and put it into a superposition of position in a laboratory full of sensitive precision-stabilized accelerometers, what should we expect them to show? To which the answers are unattractive (and hopefully will be tested soon enough by
direct experiment (at e.g. <https://www.npl.washington.edu/eotwash/node/1>)). A little more detail in <https://en.wikipedia.org/wiki/Semiclassical_gravity> or for more advanced readers e.g. <https://journals.aps.org/prd/abstract/10.1103/PhysRevD.47.45...> which corresponds with <https://arxiv.org/abs/gr-qc/9304008>.

This is far far far from the strong gravity regime near gravitational singularities. It's a problem we could test in a spacecraft in deep space, or in a laboratory here on Earth. No black holes required.

Singularities, while annoying for developing Cauchy problems as one likes to do in many areas of physics, are not immediately fatal to the theory for several reasons, including the probable correctness of the cosmic censorship hypothesis and the long term stability of realistic black holes. Indeed, at least General Relativity is a complete theory that makes a prediction about what happens at its highest energy levels (measured in curvature invariants, like Kretschmann's). The Standard Model of Particle Physics is not presently "UV-complete". (More details @ <https://en.wikipedia.org/wiki/Physics_beyond_the_Standard_Mo...>, "The Standard Model is inherently an incomplete theory.") The converse is that while General Relativity is an inherently complete theory, it requires care in encoding the stress-energy tensor, any "background" curvature, boundary conditions, constraints, energy and coordinate conditions, and so forth. It is not an easy theory at all, especially when one does not understand all the mechanisms that generate the stress-energy tensor. Its successes as an effective field theory in astrophysical applications are legion, and completely contradict the remainder of your second paragraph.

All of the above equally applies to relativistic MOND (except the last sentence of the preceding paragraph: relativistic MOND generically gets the acoustic peaks of the CMB temperature power spectrum wrong, and usually badly wrong for the odd-numbered peaks, principally and importantly because of how different MOND is, by design, at assigning pressure in equations-of-state, and how that matters before the formation of the first galaxies). Milgrom's work has afaik always been in the regime where quantum weirdness has been negligible (and indeed, for most of MOND's history was even wholly in the regime where special-relativistic weirdness was negligible).

MOND has been explored for more than fifty years, and Relativistic MOND for more than twenty years, by some of the biggest brains in gravitational physics, including Mordehai Milgrom <https://arxiv.org/abs/1310.3373>. There are endless publications about MOND even today (tiny sample: <https://arxiv.org/search/advanced?advanced=&terms-0-operator...>). Nobody working in galactic astrophysics is ignorant of it, or of the phenomenological Milgrom's law. Most theorists working in gravitation have played with it so they already know:

> exploring what modifications are needed to match observations is the way forward

So I find myself wondering: do you genuinely not know that MOND "is a thing" already (and has been for decades) in the relevant academic and professional circles?