Not exactly. The generals under-estimated the capability of the German Army early on, and Hitler was actually right to be as ambitious as he was. There was a ton of resistance from the German military about invading France. They didn't think they'd win the war, and they didn't understand how bad the military in France had gotten.

Both the military and the government pretended that they had preformed better against the French, Dutch, and Polish than they really did, and when they stormed into Russia, they over-estimated their capabilities.

The Generals were right at one very specific point: when the war was lost. The military had long since figured out that the war was unwinnable by 1944. Frankly, there were a lot of generals that thought the war might not have been winnable before the Normandy invasion. That's the thing that Hitler wouldn't accept.