To be fair to him, my partner who works in Healthcare has the same concern, and for quite precisely the same reason: if the kind of work normally done by juniors who are training/building their skills is done by machines instead, where do the next generation of seniors come from?
My response to both was that I was confident the market would fix this problem itself - people will not pay for garbage. There is a reason books are still printed by established publishers. Why buy a book when you can just print a book on printer paper yourself? Because reading a book on printer paper sucks.
I cannot imagine that machines will ever replace any work where there is any meaningful threshold for "correct". I am so intrigued to see how this plays out across the broader economy.