What makes Linux appealing to me is the extent of customizability, but I didn’t find many answers when looking up with desktop environment is them most customizable. Some say KDE is most customizable than say, Gnome, but doesn’t Gnome support CSS customization while KDE doesn’t?
I would say XFCE and Cinnamon; no two XFCE’s look alike and Cinnamon can easily be molded into something very different as well.
I see a lot of people recommending KDE and Gnome; I’ve found those surprisingly rigid, although there are more guides on how to “rice” KDE into the most non-KDE things so there’s that.