My read of the article is that the problem with Wayland is that the devs were writing specs instead of software. There was lots of planning and no doing. Remember that originally Ubuntu was supposed to be running X-Mir by default in Oct 2013.
Those days were more optimistic times for Ubuntu and they thought they could create a new display server in a year. These days Mir and Wayland seem to be at about the same stage of readiness.