I don't think packing up and moving an army sized attack is that easy. The low resources included low levels of mobility. The attack on the Psel was already an axis that was not planned originally, but developed during the battle. And the Soviet + western allied economies were really getting into gear, so that any delay meant an increase in odds, at least in terms of equipment, both quality and quantity. Frankly, I think the Germans did as well as can be expected. It is the Soviets that could have performed far better than they did. Why does everyone always fixate on possible German improvements against a Soviet defense that is reified as stiff and unchanging as a bronze statute?