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You don't even really have a simple Wayland server since they fused the window manager to it. That means every window manager has to have its own Wayland server and compositor code, likely copy pasted for added updating pain.
If you want to change your titlebars, you need to get a non-gnome (or install a workaround), replacement for your program, change your entire Wayland server, and then maybe you'll have the ability to configure it (you just lost copy-pasting on a separate program btw).