I, as an end user, do NOT care.
>A lot of the "existing functionality" that it broke has nothing to do with displays, it's stuff that got crammed into Xorg at some point whether it made sense or not.
I also don't care about ivory tower ideals of what is within the dominion of 'display' and what is not. The fact of the matter is their changes broke a ton of functionality, and instead of even trying to provide feature parity, they basically dumped all that responsibility onto the WM/DE devs.
I have no idea why the community didn't take one look at their proposal and flatly ignore them.