Earlier quoted context omitted.
thanks. this is pretty scary. guess I'll be using Chromium when that day comes, as I'd rather not run PulseAudio.
You could volunteer to rewrite Firefox’s entire ALSA backend to add multiprocess support. That’s what caused this, because Mozilla doesn’t have the manpower to rewrite two backends, and so had to choose one (with the pulse backend being preferred, as the pulse maintainers help mozilla and fix bugs on their side, while mozilla reports getting no assistance or anything from the ALSA maintainers).
Sad reality is that they are trying to not hire competent people while having features implemented well. Mozilla is vastly understaffed for the magnitude of the project.