Which is why there has been so much fuss. I haven't kept up, but has the Wayland project changed their tune on networkable graphics? I will grant that X could use some uncrustifying, but I think the general gist of the OP is correct: there is just so much that X offers that Wayland and Mir will have to catch up to (assuming they can, which requires not just time and effort, but forward thinking on design and architecture).

And as for performance, my N900, a four years old phone, runs X just fine. The sad experience I have had with software (including OSS), is that the newly born projects are almost always designed without paying attention to efficiency, usually through a lack of awareness because people are so used to fast hardware these days.