It reduces motion, but it does not remove that transition.

It is infuriating, as someone who is use to the instant switching of i3, I can't believe that it's not possible in MacOS.

My work arounds are to not use the native fullscreen for anything, and just do my best to remove window-titles/decorations from every app i use and then make them "fake full screen"

You’re not alone. Using i3 allows me to work on muscle memory without going through an observe-interpret-respond loop with every move. It really is a shame that animated transitions in macOS are non-optional. Who decided that transitions help users? It’s like tacky jQuery fade and swipe transitions on everything.