The only problem with instant transitions is that sometimes you may not notice what changed. I would like to see a UI built around instant transitions but with subtle animations that happen after to emphasize the change. Like the new content shines, or does a tiny bit of grow/shrink, but not in a way that prevents interaction. There's nothing I hate more than waiting for long transition animations (looking at you, macOS fullscreen button)
Well, stuff like this used to be encoded in HIGs (Human Interface Guidelines). The GNOME HIG, back in the day, had the parent's recommendation, as well as the rationale for it: so that the feedback is immediate, and the user can then visually see the effect that that option has.
Gating it on a submit forces a user who is looking for something & not finding it into a "try one thing, submit, evaluate, open settings, undo that, try different thing, submit…" loop, which is a lot longer.
