The protocol uses shared memory buffers and file descriptors, so it can't be just transported through TCP as-is. You need something like waypipe, which parses part of the protocol, extracts things like file descriptors that won't make sense on the other end, and then reconstructs things on the destination.

waypipe turns out not to be that complicated, it's just 15K lines of code.

Wayland should have shipped with a default implementation that had screen sharing, recording, clipboard and everything else that x11 had by default. The fact that they've thrown all that responsibility on DEs without so much as a HOWTO on how to reach parity is ridiculous. I will never understand why anyone took their effort seriously.

Well, all DEs (excepting maybe Xfce?) have members in the work groups that design the wayland protocol extensions, so it can be assumed that people are well aware of what needs to be done.

Wayland has a default implementation called Weston, but I'm not sure that any of its devs cared enough to implement the extensions which are responsible for all the other bits that you mentioned.

x11 had long time become unsustainable in multiple ways

braking changes where inevitable

all of the most relevant DE had somewhat already gutted out X11 leaving nothing behind then the interfaces

so the replacement being defined by interfaces and "every DE for themself" was just natural, for the large DEs it was already the case anyway

and for the other DEs you could say wlroot is now the common core they need because they don't have the will/time to implement everything by themself