I argue that X11 would have hyperactive development, if we did not have Wayland
Wayland was started by the X developers because they were sick and tired of hysterical raisins. Noone else volunteered to take over X, either, wayland devs are thus still stuck with maintaining XWayland themselves. I’m sure that at least a portion of the people shouting “but X just needs some work” at least had a look at the codebase, but then noped out of it – and subsequently stopped whining about the switch to Wayland.
What’s been a bit disappointing is DEs getting on the wayland train so late. A lot of the kinks could have been worked out way earlier if they had given their 2ct of feedback right from the start, instead of waiting 10 years to even start thinking about migrating.