Your point is well taken. Once the battle at Stalingrad was done...virtually every German general felt that winning the war was now impossible. That was December 1942. The only German leader who felt otherwise, was Hitler.
Early in the days of Barbarossa, a German General saw the T-34 in action for the first time. He remarked, that if the Soviets could manage to mass-produce the T-34, Germany would lose the war.