Except it didn't. In the GL programming model it's trivial to accidentially leak the wrong granular render state into the next draw call, unless you always reconfigure all states anyway (and in that case PSOs are strictly better, they just include too much state).
The basic idea of immutable state group objects is a good one, Vulkan 1.0 and D3D12 just went too far (while the state group granularity of D3D11 and Metal is just about right).
> Similarly, WebGPU could have done without that static binding mess.
This I agree with, pre-baked BindGroup objects were just a terrible idea right from the start, and AFAIK they are not even strictly necessary when targeting Vulkan 1.0.
Even if those state group objects don't match the underlying hardware directly they still reign in the combinatorial explosion dramatically and are more robust than the GL-style state soup.
AFAIK the main problem is state which needs to be compiled into the shader on some GPUs while other GPUs only have fixed-function hardware for the same state (for instance blend state).
This is where I think Vulkan and WebGPU are chasing the wrong goal: To make draw calls faster. What's even faster, however, is making fewer draw calls and that's something graphics devs can easily do when you provide them with tools like multi-draw. Preferably multi-draw that allows multiple different buffers. Doing so will naturally reduce costly state changes with little effort.