>>344107846
Well we can't really figure out how to fix basic sensory disorders at all, and the rest of applied neurology seems to be crudely blasting the brain with chemicals.
Full dive requires tapping into every sense at once and providing a high fidelity feed that mimics reality. It would probably need some kind of advanced AI to tailor the stream to each individual as well.
It's a post-singularity tech, imo, which means based on AI experts' predictions anywhere from 20 to 200 years from now. Assuming advanced human civilization lasts that long.