Robert Ancell contends that the application toolkit is more important than the display server. "The result of this is the display server doesn't matter much to applications because we have pretty good toolkits that already hide all this information from us. And it doesn't matter much to drivers as they're providing much the same operations to anything that uses them (i.e. buffer management and passing shaders around)."
Martin Gräßlin counters that by taking a look at issues created by making applications work with multiple display servers. "Also the assumption that the toolkit behaves the same is just wrong. One of the issues I fixed was Qt returning a nullptr from QClipboard::mimeData on platform Wayland while it returned a valid pointer on all other platforms. It’s obviously an application bug but the documentation doesn’t say that there could be nullptr returned or not. There can be hundreds or thousands of such small behavior differences. An application developer is not able to ensure that the application is working correctly on a distro-specific display server."