Did France overspend in fixed defenses? Was France capable of rebuffing, or holding fast, the German Blitzkrieg if those same resources had been allocated to modernizing the French army's personnel, equipment and armor?
Not much.
Robert Forczyk points out that French spending on the Maginot Line amounted to about $195m between 1928-36. Hitler spent $400m on West Wall fortifications between 1936-39.
The blame thrown at the Maginot Line glides over truly useless white elephant projects like the French Navy, which was turned into the world's fourth largest fleet to maintain connections to France's insignificant Asian empire.
Source: Robert Forczyk: Case Red: The Collapse of France