I think educators are too afraid in general of getting into some real accurate phonetics IMO. Lowest hanging fruit seems to be phonetic diagrams of where the tongue/lips should be. Perhaps normal in other peoples experience?
Phonetic diagrams aren't feedback though. You would explain how to do something correctly, but user wouldn't know what elements they need to change, unless they figure out on their own what they are doing right now. I know my teachers told me to do X when they heard me mispronounce something specific, but that's irl small group/1on1 experience.
Again, I'm curious if someone solved it. Theoretically this is within modern video/audio AI, but that doesn't mean we have the models or even organized data.