History revision is a guessing game. Most of the French troop for WWII were never born. French birth rates have been much lower than other European countries dating back to before WWI. Troops in WWII would have been born mostly 1910-1929/30. The French lacked sheer male numbers. Their fortification line was one hope to offset that short coming. But every military is better at refitting the last war in hind sight than correctly predicting the next one. Had the German gone to a trench warfare plan instead of a war of movement the French were well equipped to withstand the Germans for a very long time. But the French never got the email that the Germans were not going to play that game.