I absolutely am. Calling Wayland “something that has been broken for more than a decade” rather than “something that has been in active development for more than a decade” is also an interesting take. By that measure X.Org is “something that has been broken for almost two decades”, so let’s just not go there. And I’m not saying that Wayland magically makes everything secure. I’m saying that Wayland (or something like it) is a necessary step if we want a desktop that is secure. I have seen people propose something like nested sandboxed X servers with a single application for each as an alternative, but I think it’s probably better to actually fix the underlying problem.
That’s an interesting use case. It isn’t really anything I’ve had a need for, so I don’t know what the best way to do something like that is. If your compositor doesn’t allow it, could it perhaps be possible to run as a different user in a nested compositor, like Cage or gamescope? Also, how do you sandbox the applications X11 access? If they share the same server, then a sandboxed application can just wait for you to launch a terminal and use sudo, at which point it can inject a malicious command as root.