I said build on top of wlroots, not DWL. And I only brought it up as an example of a small Wayland compositor/window manager because the poster I was replying to wants to build their own anyway. DWL is more interesting as a learning exercise than something to use.
Xorg is still being under development, there is another fork in development too (XLibre) and you're in the comment thread for a project about a brand new X server written from scratch.
Usually things which are "no longer developed" do not have (at least) three implementations in development.
(i worked a _little bit_ on dwl) each wlroots upgrade is a pretty small diff on the dwl source. the annoying part is, as dwl is configured with patches, every patch author has to update their patch to the new 0.x, as dwl is quite minimal, and thus has no stable api. that being said, obviously, dwm doesn't have this problem :)
also, for dwl, the issue is that the initial author (not the guy that wrote that notice) is sorta mia, and he has control of the repo on codeberg, so we'd probably need to fork to be safe, and he may not want to take on project lead. (he checks every patch for merge conflicts with one another and upgrade breakages, god bless him lol)
Nearly every Wayland compositor is built on wlroots. Somehow they manage. But yeah, of course it's going to change more than X11, which is older than I am and more or less abandoned...
It's actively maintained by projects like RHEL which still have versions which are supported which in turn support X11.
Others are looking to run X11 wm under wayland with wayback, xlibre wants to keep it moving forward, and phoenix wants to replace it with a modern version.
And DWL is not super small. It's hundreds of times larger than a minimal X wm, and couple of times as big as the wm I used.
And it's C. And it'd mean I would lose my session if I want to make changes and restart it.
What you're suggesting would be to put significant effort into replacing something that works with something that in terms of features I care about is strictly inferior.