You're comparing apples and oranges. Your argument is that proprietary API's are better than Vulkan because there are less code paths, but if you go that way y

You're comparing apples and oranges. Your argument is that proprietary API's are better than Vulkan because there are less code paths, but if you go that way you need a completely separate code path for each top-level API. I think you're vastly over-stating the complexity of handling this in Vulkan. For the ray-tracing example, realistically you have one branch for non-ray-tracing, and one more where you check for whatever RT extensions you need and do ray-tracing if you have them available. This is exactly the same complexity you would have with DX12. DX12 Ultimate is a really poor counterpoint. No serious game developer is going to be content targeting only XBoxSX and PCs build for over $1200 in the last 18 months. Realistically, even if you only target MS platforms, you're probably even going to need a DX11 renderer, and the DX12 API is already quite different on XBox and PC, so that's already 3 code-paths minimum.