Second, nobody's arguing for "one size fits all". X11 proponents who point out that Wayland will not be as functional as X11 are pointing out that there are things we use that X11 has that Wayland will ditch.
I'm pretty sure someone does argue for that! Or I at least hope so (tell me if we've read my "fits all" line differently!).
I get the impression you like X11 (to the point of labelling supporters of something else "anti-X11"). X11 currently works for some, doesn't work for others.
The way I see it, X11 has to work for everyone, or be replaced for many sets of users. Currently some users are having problems with running a modern desktop because of it. The only options for a smoother experience are closed source operating systems. Basically, unless X11 can work for everyone, people will create an OSS option.
I have a hard time being convinced by your idea of one-to-one feature replacement. It would basically mean copying a system which is originally from 1984. Even with a rewrite, it's still "keep everything and add more on top". When has including as many old features as possible ever made a project work better? The difference between your optimism here and your pessimism about Wayland's actual code development is pretty stark. In reality, we do not yet know what the result will be.
There comes a point where the different desired features cannot be reconciled: it's probably possible to code a network transparent 4K video display system in principle. However, in practice it will just output junk, even with tomorrow's networks.