A dumb relay of events is useless without a clear definition of what those events are. Before the dumb relay part there *is* either a negociation at the wayland protocol level, or an unambiguous specification at the wayland protocol level, of what is relayed. Users really do not like if the same event produces different things in different apps, regardless of their DE or toolkit. Users do not want to reconfigure their input each time the display server selects a new surface. Something that emits “A” should be relayed as “A” to every app, regardless of what this app makes of “A” (and “A” is the simple case, because of ASCII).

The Wayland project consisted of untangling many things that were baked into the X11 server, including font rendering since you want to take that example, and coordinating those things via the wayland protocol and its extensions. All those untangled things, including those that ended up in a different subsystem than the display server itself, are part of the Wayland project. And it allowed display server people to focus on display things but the display server alone is no Wayland let alone an X11 replacement.

A Wayland environment can not select a modern date format because the Wayland project did not untangle the way glibc defines the date format and therefore it is not possible to negotiate a date format over the wayland protocol, just a glibc locale. And there is no point in redefining things at another level than wayland because users expect their dates to look the same in all apps. We are no longer in a world where all apps are launched in a shell terminal and are statically synchronized via shell environment variables.

Wayland is all the things that Microsoft had to bake into wslg to make gui apps work, and Wayland limitations and deficiencies show for example when it is mightily hard to convince wslg to use the correct locale and input method. The nice thing about wslg is that the host environment is free of all the legacy X11/terminal stuff, that obscures where Wayland is unfinished and relies on something else to sort of work.