Second, just because they can do something doesn't mean everyone has to agree. They have their right to make their choices, but we also have a right to judge them based on those choices. Or do you really think that neither Gnome nor PulseAudio devs got any criticism?
Third, there is a big difference between something like a sound API or desktop environment, where applications written for different ones can happily co-exist, and a display server or protocal, where they can't. This is much less like making a new PulseAudio or new Gnome and much more like making a new Linux kernel, where libraries and applications written for the Linux kernel will not necessarily run at all on the Ubuntu kernel and vice versus.