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?
For me the main difference is that KDE wants to be customized, whereas GNOME does not. You can theme gnome, but they don’t like it and will not make it easy. As for css customizations, I themed some gtk (not gnome) apps and really don’t want to do it again. The css is some weird flavor that doesn’t support half of css features and you can’t edit the “html” so targeting some elements is really difficult.