Wayland is a fairly controversial replacement for X11, written by the people currently maintaining the X.org X11 stack.
As the summary implies, Wayland been criticized for lacking significant features of X11 such as network transparency. Defenders have argued that network transparency is a minority application and that they don't like the way it's implemented in X11 anyway,
Those of us who use network transparency are rather bothered by being told that something that works fine for us (and it does, I regularly have to configure LibreOffice systems running on AWS instances, and have never bumped into any of the supposed problems Wayland advocates insist I have) are things we don't really need or want. We're not happy about losing functionality simply so that someone can go from 59fps to 59.5fps when playing Call of Duty.
Previous proposals have varied from proposals for an optional intermediary protocol sitting between Wayland and the client (apparently by people who have no idea what the transparency part of "Network transparency") and even the ability to stream the contents of Windows using H.264.
This proposal sounds, at least at first glance, to be better than those hacks. Hopefully it means they're finally taking the issue seriously.