It requires a Qt Toolkit for UI upgrade and developers prefer to not constantly be spending labor on chasing the current version of every dependency when they could be doing more artsy things.
AFAIK Krita 6.0 plans on bringing Wayland support & the upgrade.
Could you elaborate what you mean by "doesn't have Wayland"?
Krita works fine on Wayland (I just finished using it to scribble out a comic strip, in fact), but is there something specific you're finding that is broken?
(commenting so someone corrects me and so they reply your question) i guess they will work on it when they port it to Qt6? I heard they will be porting Krita eventually but haven't heard when they're going to do it.
I did not know Krita does not have Wayland though, I used to use it with Wayland without any problems whatsoever so not sure what that means