Wayland originated, AIUI, because we've got layers upon layers of complexity and indirection to bend X11 into what we want on a more recent environment, and building a system with more awareness of what the constraints are in recent systems lets you implement things much more cleanly than those levels of complexity (or, at least, not much worse, if you're using XWayland).
(Of course, it's not implausible that in 20 years or less, we'll think of Wayland as requiring lots of kludges and hacks to do what we need then, but you can only plan for known knowns and known unknowns.)
In the long run, it always comes down to emulation, regardless of system (e.g. Win16 is no longer a part of current Windows). Perhaps ReactOS has some promise w/r/t old Windows executables...
And on Windows, a 10 year old program NOT working is extremely rare.
Hell, a 20 year old program is most likely to be running too (most common issue would be the installer but usually it can be worked around).
> Unless you only have libc as a dependency but I doubt that for a graphical application.
You can also have xlib as a dependency and it'll work since unlike whatever madness is built on top of it, the X11 API is stable (but of course modern developers dislike that stability and want to replace it with Wayland that breaks everything again so they have new toys to play with). Example: https://i.imgur.com/YxGNB7h.png (from an old toolkit of mine, showing the same binaries running in 90s RedHat and last year's Debian).