Wayland was started primarily by those who were maintaining X11. There is almost nobody who is both capable of working on X11 and wants to work on it.
The redesign also reflects their priorities. The best analogy I can come up with is imagine a small group of people maintaining an old car frame and mechanical workings. They work hard to keep the engine running, but it's in a chassis with leaf springs and direct steering. It also has lots of vestigial things like a hand-crank even though most people have been using an electric starter for years. Other people use this as a platform to make complete cars with body &c. but this is both too much and too old for the small group to maintain themselves.
So they build a new, more modern engine and wait for other people to build a car around it, which is more sustainable amount of work for them. Lots of other people complain that the engine isn't a car, and when they use the engine with one brand of car, the brakes don't work and when they use it with another brand of car, the steering doesn't work. This makes sense, since previously the underlying platform implemented much of those, but now it doesn't and everyone is figuring out how to build those and couple them to the new engine.
Eventually you reach the point where each brand has created its own brakes, suspension &c. that mostly work about the same, but the only actual common component is the engine now. That's about where we are today.