There's plenty of reasons to start your own fork that you have full agency of, as long as the OSS License is maintained anyone will be able to benefit from any new features they want to make use of.
Today, legacy KHTML maintainers are boxed-out of upstream decisions that might prevent Manifest v2 from swirling down the drain. I'd argue the story isn't very beautiful anymore.
So while technically not the same story as if it was a direct fork of X11, practically they have the 'obligation' to support X11 indefinitely. KDE trying to kill X11 too is the same exact EEE that you mentioned as a sad story in regads of KHTML.
KHTML is tragic because it had willing developers working for the public good. Jack1 and X11 are not tragic, because their developers were already drafting transition plans to depreciate their libraries.
Also sysvinit is straight up obsolete software. Even if you hate systemd, there’s just no reason to use sysvinit because things like OpenRC and runit exist.
In addition, the adoption of systemd has lead to needing to maintain less init scripts because systemd units are just more portable. It used to be that every single distro and even versions of that distro required specialized init scripts for every application.