Libraries are a thing

> because the APIs are DE/Toolkit specific

That’s false in itself, what do you think Wayland protocols are? They might add some DE-specific protocol for themselves, but I don’t see why that would be a problem.

> standardization that X11 offered

What standardization? A single implementation that does its thing is not a standard, by definition.

> Also X11 was never "monolithic" but in reality completely modular

But let me guess, you think that systemd is a huge monolith, right? Also, a wm is very trivial compared to the rest, they can easily be a lua extension and that’s it.

X is monolithic, because they had to pry printing and shit out of it over years of hard work.