That's because DirectX 11 and older have a single thread draw submission queue which is being a bottleneck. DX11 still dominates - right now there are five (5)

That's because DirectX 11 and older have a single thread draw submission queue which is being a bottleneck. DX11 still dominates - right now there are five (5) DX12-only games and only a handful announced, because it's so completely different you have to re-engineer significant part of game engine to get the benefits.