Didn’t that happen a long time ago which is how we got MATE?
I no longer follow developments in GTK based DEs much because nowadays KDE Plasma is so clearly the best choice for me, but it has long been my impression that GNOME just wants to be its own thing that doesn’t really care about anyone not using GNOME. This is probably because the main role of GNOME is to be the DE for installations commercially supported by Canonical, Red Hat, etc.