Well, in a way, that is also Linux's strongest advantage, so you win some, you lose some.

That's actually the biggest advantage of Linux.

if we're talking about X the standard and not Xorg the implementation, shouldn't the former be the grand unifying vision?

X the standard and Xorg the implementation have been one and the same thing for a while.

But X is just a component for the system, and what is lacking is a vision for the system as a whole. Actually, unifying visions have emerged for many facets of the system (as proven by the success on the server and embedded space), just not for the desktop.

I think he's talking the about linux adoption not being down to X but there being no long term vision for linux as a whole. Perhaps there are not enough designers and artists on board to make the linux desktop woo business. It's not always decent APIs that win.