And don't forget--X11 is a networked protocol. It's still easy to run X apps from a server to be displayed on a local dumb client. But much like the evolution of the X server itself, the GUI and toolkit projects (Gnome, KDE, Wayland/Weston, etc) have neither the time nor inclination to invest in this use case. And so there's been a slow, two decade-long regression in this regard. And it's only going to get worse.
People who want to see Linux on the desktop may be more interested to see this happen.
There's also a number of companies selling desktop terminals you can connect to anything running NX. (Or some other server)
Unless it is easily available, it is not going to be used. As soon as you get into desktop terminals, there is dependency on an outside vendor which then becomes a vendor lock.