Currently, it's not. That does not make current efforts bad. I think they are quite nice.
They just do not yet actualize the vision X did and does today.
Whether that is wanted / needed is also an open discussion at this time.
As far as I can tell, the original vision of X was to unify all the proprietary Unix vendors with a standard windowing protocol. The network capabilities happened because they wanted to support dumb terminals connected to mainframes. Most of those proprietary Unix vendors are now gone. Currently it's not clear to me what role X is supposed to have, if any.
We may find or choose for that to not be a thing.
Ok, fine.
The X window people did make that a thing and the end result is powerful and flexible.
None of that makes efforts like Wayland bad. They aren't.
But they, by your own definition, are a subset of what X is too. They aren't thinking it through, by design. That is OK.
My own personal take is that most compositors won't because X does not represent multi user graphical computing in the way that most people use it today. That role is fulfilled by web applications.
I can't speak for all the original X developers but TFA seems to suggest that they didn't think it all through.