It’s not that simple. If you want up to date GTK (aka GTK 4+ ) the Gnome team (let’s face it, most Gnome devs are also the main GTK devs AND the main Fedora contributors) has coded it in such a way that it is almost impossible to avoid a Gnome look and feel. Of course the Solus team mad a bad decision (one that now also Pop! has done) and based their DE so close to source that it’s not actually a Fork, just a “shell” on top of Gnome.
Anyway, I have been arguing for quite some time that GTK needs to be forked. I doubt Cinnamon or Mate will ever move past GTK 3 anyway, since their whole existence is mandated on NOT being Gnome or forced to look like Gnome.
The GTK devs / Gnome devs are really more and more a closed ecosystem where they no longer care about any impact on Linux as a whole, only about Gnome and don’t really care what happens to anyone else using “their” toolkit. They’re basically Apple, but in FOSS clothing.