Pretty sure WebGL2 doesn't have true compute shader support. It's more a jack where you can write to a texture buffer with a fragment shader to imitate a compute shader. True compute shader support is supposedly in WebGPU
Not bad at all! WebGPU has compute shaders in the base spec, and it looks like 66%+ of internet traffic already supports it: https://web3dsurvey.com/webgpu
By the way, if you are running any high-traffic websites you can donate your users' device data to web3dsurvey (with a simple JS snippet). I'm sure it will be appreciated.