Well, in practice we can't really confirm a theory so much as "fail to reject" it. There's a zoo of gravitation theories out there and this new data weeds out some of them.
The problem I see with the "confirms GR" language is that the new data also fails to reflect some of the MOND models, but are we going up say that it "confirms MOND" as well? That sounds really misleading to me.
You’re absolutely correct. I’m still really skeptical of dark matter. It just feels more like a massive black box of not understanding what’s going on than non-visible matter.
I'm not sure how most of the alternatives are any better. MOND is a massive black box of not understanding what's going on with gravity.
Dark matter: Some sort (or sorts) of particle that interacts gravitationally. It can't interact via the strong or electromagnetic forces. If we're very lucky it interacts via the weak force as well and we'll be able to directly detect some, but there's a good chance that it doesn't and we'll only ever have the indirect detections. And there are a lot of indirect detections that the current theory (Lambda-CDM, henceforth ΛCDM) predicts: the anisotropies in the cosmic microwave background, the large scale structure of the universe, galaxy rotation curves, gravitational lensing where no visible matter exists to create the lens, velocity dispersions of elliptical galaxies, galaxy cluster radial velocity distributions, galaxy cluster x-ray spectra, baryon acoustic oscillations, redshift survey distortions, Type Ia supernova distance measurements, Lyman-alpha forest measurements, and now the measured speed of gravitatonal waves.
Any alternative to cold dark matter + dark energy needs to agree with all the observations. Not just some, ALL. ΛCDM does. Some alternatives agree with parts and make no predictions about the rest, so they can't be eliminated (eg entropic gravity). But ΛCDM is currently the best fit for the observations.
I am not a physicist. I acknowledge that we need a way to unify QM and General Relativity, so one or both of those two must be incorrect. I just don't think that Dark Matter is an hypothesis thing to discard, given the evidence.
The problem I see with the "confirms GR" language is that the new data also fails to reflect some of the MOND models, but are we going up say that it "confirms MOND" as well? That sounds really misleading to me.