This is not to say that computers aren't used in monitoring plant status, quite different from control. This provides data. This is certainly true of all engineering fields. Any good history of engineering will suggest that many designs never are marketed because of an unending sequence of irremediable faults. This is teleological.
Confidence is an intuitive assessment of reliability.
To obtain high confidence in the number of faults requires observing very many errors, thus lowering one's confidence in the product. To obtain high confidence in a product requires observing very few errors while using it. Contradict me if you can. The unprecented success of the Viking mission was due in part to the ability of the flight software to operate in an autonomous and error free manner. In the initial stages of the Viking flight program development, the decision was made to test the flight algorithms and determine the timing, sizing and accuracy requirements that should be levied upon the flight computer prior to computer procurement.