X11 is absolutely NOT legacy. It's still better in any relevant way than wayland. Freedesktop just wanted to kill it for weird reasons. But Xorg forks like Xlibre are very active and there are even new implementations like YServer. I still use X11 for every new setup.
> Freedesktop just wanted to kill it for weird reasons.
I wouldn't wish to defend them, but by all accounts the biggest reason is because Xorg's code quality is quite poor, which is (if true) somewhat fair. I wish they tried replacing it without breaking everything and shipping the terrible design that is Wayland, but the goal of replacing Xorg is reasonable.
The great thing about Wayland is that if someone comes up with something better, this time around they can just implement that without the friction coming from X Window System's custom driver layer.
The Wayland ecosystem just runs on top of standard kernel interfaces and that's a really huge win for any future protocols.