Am I reading that right? It makes API calls that go through 5 different layers before actually getting rendered? That's kind of crazy. I'm surprised it works, although I guess the underlying libraries are solid enough that it shouldn't be unexpected.
This was the pipeline in Proton for macOS (I'm not sure if it's still is the case, been quite a while since I checked).
There're some D3D implementations over Metal that could skip the Vulkan layer but none implement the old D3D8 so you'd still need another layer that implements e.g. D3D8 over D3D9-11. Also, DXVK and MoltenVK have got a lot of traction and fixes on their own, so they're probably the most accurate pipeline for D3D on Metal.