It sounds more like a confirmation of GR. Mass-energy tells spacetime how to curve through gravity, and spacetime tells light where to travel.
The title of the article "Colliding neutron stars falsify some theories of gravity" is accurate, but the theories of gravity that it falsifies isn't the popular mainstream one (Einstein's) that, let's face it, we've all been secretly hoping to take down. Instead, it falsifies some of the new challenger (MOND) theories.
I, for one, welcome our continuing Einsteinian Relativistic overlord theories of gravity (at least when it comes to dark matter)
Please ELI5 what benefits follow from taking down the GR-based gravity theory?
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.
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.