And then the thing is, how do you train new employees? Any juniors will be useless.

Year, or two of unpaid internships? It's nothing new. In my country it works like this for doctors or pharmacists - they have to do half a year of unpaid work if they want to get diploma (and I use work and not internship for reason) Because as a junior you don't bring anything of value to company, you're a loss to them.