What I am saying, in the terms of your example, is there is no viable path for most janitors, even if they had all of the necessary intelligence and ambition, to become surgeons.

The typical path to surgeon might look something like this:

High school -> Pre-med -> Med school -> etc. -> surgeon

The path from janitor to surgeon might look like this:

High school -> Married -> Janitor -> Family -> Quit job to go back to school -> bankruptcy, divorce -> janitor

To return to the topic at hand, it's entirely fair for top executives (or surgeons, etc.) to be paid their value, but only if it's also possible for others to try to achieve the same value. Path dependence breaks fairness.