MoltenVK is a commercially sold product with
some very strong words in the license agreement about what you can and cannot do with it.
RPCS3 is GPL2-licensed free and open source software. MoltenVK's license and the GPL2 are mutually incompatible.
If you want rpcs3 on macOS, complain at Apple for modern graphics APIs or install Linux/Windows via Bootcamp. It's not rpcs3's fault Apple refuses to update past OpenGL 4.1 and refuses to allow Vulkan at all.
It appears that MoltenVK has gone open-source since the last reply to this post.
Is there any work being done on a macOS binary or distribution? Is it possible to build your own from source at this point?
Work has been done to get RPCS3 booting simple homebrews by gfx-rs
https://gfx-rs.github.io/2018/09/03/rpcs3-dolphin.html
But nothing else ever since due to hardware limitations on Metal itself
It's really a waste of time too when you'll always end up with a nerfed version due to system limitations when you can just install a Linux or Windows distribution
I don't think LLVM is working on MacOS, and current Vulkan render shouldn't be working too, even with MoltenVK
You should be able to build it though