I might be mistaken, but isn't this what libraries like winit exist for? It might not be just for wayland, but it seems like it supports everything you mentioned other than drag and drop.

Generally yes (or GLFW, or SDL), but the Wayland project shouldn't delegate the job to burned out hobbyists (who will think twice before wasting their time with bad APIs). This client library should really be a mandatory part of each Wayland install as a system library, not part of the application. And most importantly, the Wayland project needs to start eating their own dogfood, or things will never improve.