The irony here is that AMD absolutely refused to support OpenGL (a standard) properly and would wish it never existed and Direct3D (a Microsoft-only API) was the only 3D API to have ever existed. No, seriously, their OpenGL support has always been atrocious. Fair enough, it used to be worse (OpenGL 3 forced them to start maintaining their OpenGL drivers again) but it's still atrocious in comparison to Nvidia's support for it.
Of course the fact that basically any game that wasn't made by id was using exclusively DirectX wasn't helping matters, but if Nvidia can keep OpenGL in good shape, so can AMD (or ATI back in the day). I guess it may have to do with the fact that some of Nvidia's biggest clients are involved in the CAD business and CAD software does expect the less common parts of OpenGL to, um, work.
Isn't AMD partnering with the OpenGL team to do their Vulkan thing?