X11 was started in 1984 in MIT. That means, when Wayland was first conceived in 2008, there had been 24 years of X development.

I guess Kristian grossly underestimated the effort required to write a full features Display manager.

FWIW, innmy career the times I've had to perform very impactful changes in software, I always start from the current codebase and remove/simplify stuff.

As an example, once I was in a company that had built a huge Ruby monolith which was not scaling at all. It had APIs for everything, including "high frequency trading" in the same codebase server, under a METAL aws instance (that's how they scaled).

What we did initially was simply copy the repo N times (sign up, compliance, risk, trading, etc), spin up an copies of the same server and use a balancer to route APIs to the different boxes.

Then we started removing unused stuff from each of the repository to specialize them. Fiinally we simplified complexity on each separate codebase.

I would have approached X11 codebase similarly.