Edit: Yep KDE is the most customizable full desktop environment. I gave Gnome a shot but like KDE A lot more with desktop effects and kwin scripts.
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?
KDE is the correct answer. I guess you could also learn coding, and then any piece of open-source software would become “customizable” to you…