>you either have to add GTK as a dependency to get the "correct looking" titlebars or spend useful development time writing shitty, non-native looking window decorations just for GNOME users

That's a false dilemma. You don't have to do either of those. The alternate solution is mentioned in that issue: use libdecor. I'll also note, if you refuse to use any of the system's UI and you insist on implement everything yourself directly on libwayland then that's an entirely self-inflicted problem that you created. Libwayland is fairly low-level, it isn't a game development API. Besides window decorations, you'll have lots of other deficiencies and things you have to spend development time on. That's what you volunteered for, GNOME can't help you with that.