Wayland is far from mature, even with xorg-xwayland.
I personally use it with (fairly uptodate) KDE/Plasma on a Intel Iris Xe Graphics, and still get some annoyances.
2) Nothing in the parent comment even mentioned Wayland, unless it has been edited- they're saying that people don’t run X.org as root these days (which I am not certain of, since I haven't been running it for so long)
If you try other desktops that use Wayland such as Gnome or Sway you will find far fewer issues.
Wayland is designed to block this feature. Which means it will always remain a niche, only useful for those running multiple monitors with different refresh rates. And even those people are limited to AMD GPUs. So that's a very small niche of a very small niche.
Most people just want something to display their windows. Those things are cool, sure, but they probably come at some cost.