The other factor I read regarding the difficulties of resurrecting the Saturn V engines, was that they used a lot of mechanical feedback control systems to regu

The other factor I read regarding the difficulties of resurrecting the Saturn V engines, was that they used a lot of mechanical feedback control systems to regulate fuel flow etc. Modern engineers can understand them in theory, but they'd just use a micro-controller for anything that complicated, so they don't have the same fluency in those systems as the original engineers.