I've written more extensively about this here but here's an analogy that should get the point across a bit better: Wayland is just a protocol, just like HTTP. In both cases, you have two sides with very different roles and functionality. In the HTTP case, you have the server (e.g. Apache) and the client (a browser, e.g. Firefox). The communication protocol is HTTP but both sides make a lot of decisions unrelated to the protocol. The server decides what data is sent, the client decides how the data is presented to the user. Wayland is very similar. The server, called the "compositor", decides what data is sent (also: which of the clients even gets the data). The client renders the data  and decides what to do with input like key strokes, etc.
Asking Does $FEATURE work under Wayland? is akin to asking Does $FEATURE work under HTTP?. The only answer is: it depends on the compositor and on the client. It's the wrong question. You should ask questions related to the compositor and the client instead, e.g. "does $FEATURE work in GNOME?" or "does $FEATURE work in GTK applications?". That's a question that can be answered.
Of course, there are some cases where the fault is really the protocol itself. But often enough, it's not.
 albeit it does so by telling the compositor to display it. The analogy with HTTP only works to some extent... :)