Yes.
> Is the reason you can't accomplish that today bc APIs haven't been created or opened up to allow such workloads? Are there not lower level APIs available/exposed today in WebGPU that would allow developers to begin the design of browser based ML frameworks/libraries?
That is correct, there is no way before WebGPU to access compute capability of GPU hardware through the Web. There have been some hacks based on WebGL, but those are seriously limited. The fragmentation of the existing API space is a major reason we haven't seen as much progress on this.
> Was it possible to interact with the GPU before WebGPU via Web Assembly?
Only in limited ways through WebGL - no access to workgroup shared memory, ability to do random access writes to storage buffers, etc.
> Other than ML and graphics/games (and someone is probably going to mention crypto), are there any other potentially novel uses for WebGPU?
Yes! There is research on doing parallel compilers on GPU (Aaron Hsu's co-dfns as well as Voetter's work[1]). There's quite a bit of work on implementing Fourier transforms at extremely high throughput. Obviously, physics simulations and other scientific workloads are a good fit. To me, it feels like things are wide open.