FOSDEM: The Wayland display server

'... is a goal for the display server' does not follow from '... is a goal for a popular OS'.

I agree that the latter is essential, yes. But window decorations are only one part of the battle if your apps are using different toolkits which look superficially different, have a different button order, disparate configurations, use different file chooser and/or print dialogs, and in general are designed by two completely separate teams of people who have completely different ideas about UIs.