Not touching DX12 is unlikely to do with favouring nvidia, its more likely that DX12 is a very limited market, DX12 is windows 10 platform exclusive.
The best thing for consumers is a mass migration of developers to vulkan but for some reason people on this forum seem to like DX12.
If I was paying a developer to make a game I wouldnt have them waste time on DX12. Its a dead end technology. I would pay them to use an API that will support the largest devices possible, so either DX9 or vulkan.
There is a reason only a few very large budget AAA games have even touched DX12.
DX12 is actually making my battlefield 1 experience on my 1080ti a whole of a lot better. My 4770k @4,4ghz is choking hard on even 32 player servers in DX11 on certain maps(singleplayer is perfectly fine though) but DX12 has helped a good deal with that. Now whenever i enter a new round i get 5 secs of lag and stutter but then we are good to go vs in DX11 where i would stutter on and off all the time. Never thought i would say then cause dx12 in bf1 on my rx 580, rx 480 and r9 290 was dreadful and not playable.