X11 is a decades old protocol. People kept saying “can you please support this one new hot thing?” and the devs were like “fuck, let me think of something. [furious duct taping] There, it works! Kinda.” Yes, it’s “stable”, by some definition of stable anyway. Also with loads of technical debt. You can keep extending it, but it’s a painful, janky process every single time. Wayland is a clean break from all of that with a more modern approach. But, of course, it’s newer, and with a clean break you want software to be ported over to best utilise Wayland, and there’s going to be a lot of work until you can finally drop the X11 compatibility layer. But I don’t think there’s anything wrong with the idea of X11 backwards compatibility at the moment. Or staying with X11 until Wayland runs on your hardware. But when the app toolkits eventually support both, I think targeting new software exclusively for X11, or further development of X11 itself, is starting to look less and less sensible as time goes on.