GTK was a GUI toolkit, it was DE agnostic and also cross platform (though it looked like shit). But as we can see from your comment GTK was captured by GNOME to be a GNOME exclusive project, if a change broke XFCE , GNOME people pretended they do not know what an XFCE is.
Did you know that
GTK was a cross platform tookit, even on Windows and Mac OS? Andf you did not had to install GNOME on Windows to use a GTK app, because it was a tooklit for making apps, and GNOME was a project that combine GTK apps, and a window manager to make a DE.
Many apps ported to Qt so I don't think there is a chance that GTK will get a viable fork, Qt will be the only cross platform toolkit
Nice, the now popular dev worldview "break things, and break things often". Just for the sake of breaking. I love it, why didn't we stumble earlier over this magnificent piece of discovery.
In other news, if you use green paint, it'll paint things green.