That's Xorg. X11 is dying because Xorg is dying and Xorg is dying because all its developers quit and went to Wayland. There's Xlibre too but it's a shitshow. Any one of us here could continue Xorg maintenance but we're not.
I think Phoenix[0] is a promising project: it's an X11 server written from the ground up, with security and legacy feature removal in mind. It's basically what Wayland should have been IMO. We didn't need a new protocol, at most we needed a new implementation of X11.
