Notably, it's unusually hard in that actual practice on humans is still a necessity since there aren't good enough training analogues to substitute for real cases, so even if you managed to scale the basic training it's still an unsolved problem to scale up the number of doctors rapidly in safe way.
E.g. you can't just educate 10x as many heart surgeons without actually having 10x as many cases for them to scrub in on that you have experienced heart surgeons to lead on unless you're prepared to kill a lot of people in the process.
