> Gravity is very similar to magnetism
The analogy doesn’t help, even ignoring that what we experience day-to-day is more like an electric field and there is a different gravitational analogy for magnetism, AKA gravitomagetism. It’s harder to notice than gravitational time dilation.
> easy via fields
Only for people who find non-Euclidian geometry that mixes time and space and is defined by a bunch of 4x4 tensors to be “easy”.
> [particles bad fields good]
“Particle” is a convenient human-scale name for things, but everything’s fields these days anyway. Even the Higgs.
In fact, GR is field-only — it’s QM which says “by the way, those things you call particles are a certain type of excitation in a field” and “if the gravity field has a particle it must be a massless spin-2 boson, also every massless spin-2 field is indistinguishable from gravity”.
> doesn’t explain dark matter
Doesn’t need to. It says there’s something to look for. GR is “stuff does X”, the observation is “X”, so there must be stuff. We’re can’t see stuff, but GR doesn’t say we have to be able to see it.
> fast rotating magnets
I don’t know what you’re referring to, the closest pattern I am matching your words to is Podkletnov whose work was never reproducible by third parties, and you can bet SpaceX will have tried.
> better gravity field theories out there, but they are lacking experimental verification
Science doesn’t use verification, it uses falsification. When an hypothesis can’t be falsified even in principle it isn’t science; when it can but only in principle, it’s a hypothesis; when it has been tested and the attempt to falsify it results in evidence that persistently doesn’t falsify it to a standard of statistical significance, then it gets published and perhaps elevated to the level of “theory”.