what if they decide their duties are brain surgery?

In your world the only thing keeping janitors from doing brain surgery is the current corporate structure?

Like the nonsense a peer post to yours is spewing

Which parts are nonsense

but if your philosophy suggests that brain surgeons can get told what to do by janitors,

It can’t.

Now, what do we do about brain surgeons and the cost of healthcare

The government pays for it like in most wealthy nations