The fundamental reason it can't tell if the drink is correct is that "correct" is in the eye of the beholder. You cannot trivially formalize expectations any random human would have of a drink made by human.

You can, however, force people to lower their expectations until they can be trivially formalized. That's what happens with tea/coffee vending machines. The dispensed drink is really bad, but it's uniformly bad, and since people don't expect quality coffee from a vending machine, they don't complain.