The problem is that input and localization were totally inadequate under X11, leading to the creation of an horrific amount of *partial* *incompatible* workarounds (ie one could fix some extremely specific use cases, at the expense of all others).

The Wayland authors (most of which used to maintain the old totally inadequate mess) tried to streamline the situation to recover maintainability, but sort of stopped half way, due to the pressure of shipping something, and probably under the influence of their allies Gnome-side (perfect is the enemy of good, just forbid all the use cases we do not care about, like HiDPI was forbidden till market pressure made everything is 96dpi untenable).

Input in Wayland is a lot better than in X11 but (for example) the streamlining did not go as far as dissociating input methods from locale (state of the art in Microsoft Office circa 1995, then generalised at the OS level), dissociating date formats from locale (which is why Linux is state of the art UTF-8 side but unable to adopt same-epoch ISO 8601 = rfc 3339) nor providing a clear architectural nexus for all the input behaviour fine tuning some were used to. To be clear X11 did not provide this nexus either is was all hacked and workarounded over time.

But Emojis and multimedia keys work fine in Wayland. The streamlining was sufficient to fix this use case.