The French Generals were all in the 60s, well past their best. Hindenburg was nearly 70. We make our troops retire at 55. So if not formally senile, the age of the commanders was certainly a factor in their intransigence and sloth in adapting.

The uS impact was not on the Germans alone: 1917 was relatively quiet because the French army mutinied and needed the arrival of the Americans to recover some morale. Had they not joined in, it is not impossible the Germans might have won.