I'd be curious which design decisions you thought were awful and were difficult to turn off? I've always though UIs across all OSes are very inflexible (e.g. on a Mac, you can't change command-tab to alt-tab, and can't cycle same-app windows without a separate keybind), so I'm not usually surprised when things are difficult to disable.

My only negative experience with Gnome was not seeing which apps were open at a glance (need to alt-tab and tile all windows). This is mainly a "what I'm used to" kind of thing though.