Wayland is definitely on the side of not breaking userspace, though. The API design, xWayland compatibility layer, and recent focus on protocols to fix missing functionality from xorg are all designed to make Wayland a seamless transition.
Otherwise we’d have been using Wayland as the only option for years now.
There are good reasons to break userspace sometimes. If we would never do so, we would stuck on X11 forever.
Linus would like to have a word with you
No, because the kernel has a different goal than most other software. Linux agrees that breaking the userspace from userspace is sometimes necessary.
Wayland is definitely on the side of not breaking userspace, though. The API design, xWayland compatibility layer, and recent focus on protocols to fix missing functionality from xorg are all designed to make Wayland a seamless transition.
Otherwise we’d have been using Wayland as the only option for years now.