X11 is stable, mature, multiplatform, excellent software - wayland is not cross platform nor stable.
It's also technically cross-platform, as evidenced by FreeBSD's support for Wayland compositors. But it's not its goal either, the goal is an excellent Linux desktop, not something that serves the 17 people in the world that routinely run the same exact desktop config on Linux and non-Linux PCs.
X11 used to crash all the time, especially after an update, back when it was being vibrantly developed. It's been a lot more stable since it got abandoned. I've not had a crash in 13 years.
I've been using Wayland for two and a half years and it's been more stable than X11 that I've been using prior for years.
Fact is still that wayland does some things better, and a bunch og other things worse.