In actual practice, much of Germany's early success came from defensive tactics (as a tool of an offensive strategy), NOT offensive. The Germans would advance rapidly, seize a strategic location before the opponents were ready to oppose the attack, set up machinegun and artillery "killing zones", and then defend it against the inevitable counter-attacks. In the mass confusion of the early war advances, it worked. Once things were allowed to stabilize and there were no easy advances into poorly defended positions, as well as less of an inclination to automatically launch human waves against German positions, things got bloody and expensive, and the German advances stalled. The land mine also had a profound impact on the success or failure of Blitzkrieg, and the Soviets utilized a staggering quantity of land mines to slow the German advance.
Intelligence went from a strong point in the early stages to a weak one, as the attrition rates ground down the scouts, and fresh recruits attempted to do the same tasks that had been allocated to experienced teams. Fuel restrictions limited aerial reconnaissance as well. As more and more of the details of the war were directed from the top, and local recon reports were "overlooked" if they didn't support the "plan", there had to be a sense of futility: "why bother". Possibly as a result, the Germans were too often totally ignorant of what the Soviets were doing, when even a cursory look from the air would have spotted things of major concern.
German intelligence was quite strong at front line level. But the higher the command level, the weaker it became. Barbarossa is the ultimate example of an intelligence f****up of the highest order, or the failure to realise that already in 1939 the Poles had broken their codes. This was the situation in 1939, and it remained so until the end of the war.
German leadership was focused only in operational warfare, everything else was just auxiliary stuff better left to paper-pushers. With such an attitude, they could've won wars in the XVIII or XIX centuries, but not in the XX century. Hitler had a point when he complained about the narrowmindedness of his generals in this respect.
In his postwar memoirs, Guderian reproduced the map with the deployment of Soviet forces that the Germans had used in July 1943 when they launched operation Zitadelle. As David Glantz observed, in this map there are seven whole Soviet armies completely absent, as German intelligence had failed completely to detect them: the entire Steppe Front and the reserves being held in the rearguards of the Bryansk and Western Fronts for launching the Soviet counteroffensive (operation Kutuzov). With this level of incompetence at intelligence gathering, it's remarkable that the Germans achieved so much.