If a relatively simple algorithm was not safe because of bad engineering decisions (or bad management incentives, whatever the case is) - then wouldn't a much more complex system be even more likely to have hard to discover corner cases and failures?
I think the use of human pilots complicates a system. You are relying on a component to the system that is susceptible to tiredness, distraction, threats, rage, revenge, self destruction, and sudden death. Complete automation would replace one extremely complex and unpredictable component, with a less complex and more predictable component.