I'm told they left out color calibration support, too (as I read it, there's no way for calibration apps to control, or even know, what compensation is applied when they're trying to measure things). Oh, and client side window decorations still around, giving up on the chance to fix an ancient security hole.
So no good for games, no good for professional graphics, no good if you don't see well... basically no good if you're any different from the people who hacked it together.
But, hey, with any luck they cut down on the screen tearing that I've never noticed.
Color management support, though taking a long time, is moving along[1], and compositor implementations have recently started appearing. Device calibration support is a different question, but a much more specialized one.
Wayland is an extensible protocol. The core is literally just "here a buffer", but it has several extension in various phases that can greatly extend its capabilities. This way, a Wayland compositor can be used as a kiosk screen for a single program, or be a full-blown compositor+window manager, all relying on standard Linux interfaces for the display part.
Color calibration can absolutely be retrofitted into this (versioned) protocol, and there is work ongoing.
It's unfortunate that colour calibration took a while to be fully implemented (xx-color-management-v4 landed on most compositors half a year ago I think, though LTS distros may need to wait longer to get it).
That being said, thanks to Nvidia I never got colour calibration to work right in X11 either, so I have no horse in this race. Would be cool to finally get HDR working for the first time, but I don't know if that'll ever happen on Linux with Nvidia hardware. Guess I should keep dual booting for HDR content until either Windows 10 dies off or I get new hardware.
I do actually notice the lack of tearing in Wayland, especially under heavy load. Used to annoy me to no end to see my windows tear when just dragging them across a 1080p screen. I don't know if it was an Intel driver bug (I tried all the config settings) or something X11 specific, but Wayland did finally fix the tearing issues I had.
I haven't noticed any problems with colours in either Gnome or Gamescope (except for the lack of HDR, of course, but that's also true on X11) so whatever is causing issues for you seems to be DE specific. Looks like we both have issues other people never encountered, that's what makes graphics stacks so impossible to debug and code for.
If you control what goes into a distribution, you can not drop support for stuff that's working and already implements those needs in favor of whatever you pull out of your butt.
If not now, soon. Gtk itself is entirely dropping X support. And it's not their fault of wayland is so incomplete but I do wish people like them, and distro managers, would realize that the waylands are not actually replacements for X yet. And they might not ever be if you're visually impaired.
So no good for games, no good for professional graphics, no good if you don't see well... basically no good if you're any different from the people who hacked it together.
But, hey, with any luck they cut down on the screen tearing that I've never noticed.