That doesn't answer the question. Assume today is not the stopping point, and that we end up with super-intelligent theory building AIs. Better than any current-day human. And better at explaining, creating visualizations, etc. than any current day human.

Why is it a problem that the professor is now a robot, and that humans could spend arbitrarily long learning from it and even after 15 years of masters-style advanced graduate lecture courses still have deeper still levels of the topic that the AI could teach them?

And if they never do reach that level of ultra-competence, well, then we found the niche for humans to continue to exist within.