These extremes exist, and GR predictions are better than Newton’s in those cases. Closest to home is mercury’s perihelion drift. We have observed black hole mer

These extremes exist, and GR predictions are better than Newton’s in those cases. Closest to home is mercury’s perihelion drift. We have observed black hole mergers, gravitational lensing, and GR is also an essential component in understanding the universe’s expansion(that we know from redshift and the CMB). Likely MOND will address these, but Newtonian mechanics will not get you there.