That's fine, sticking with X is a totally acceptable option. If they _want_ to move to Wayland, though, and it's missing something they need, then of course they should help work on that thing.
Given that these issues has persisted for so long and that they seem solved in Gnome and KDE...
Not accusing you of full NIH, but are there any technical reasons for not just reusing/leveraging kwin or whatever Gnome uses, instead of creating your own compositor library where all these issues has to be solved, yet again?
kwin and Gnome's solutions aren't reusable on other compositors. Gnome is awful at making their stuff reusable. KDE is much better, but their clipboard stuff isn't reusable, and Sway's likely won't be either due to the nature of the problem. There are plans to collaborate more with KDE on reusing KDE components in Sway and other compositors, which both parties are excited about.
So: if there isn't a WM for Wayland that allows their workflow, then they will stick with X.