I think one should first consider what went wrong with French leadership.
Age may well have been a factor. Elderly gentlemen have less energy and less desire to "rough it out" than younger men. But this is not the only difference.
French leadership was also based on their doctrine and command & control facilities.
The French system was based on the Petain principles that "fire kills" and "artillery kills and infantry occupies". The French wanted to fight the conventional 1918 battles which had allowed them to win. Instead of unrealistic offensives which just got a lot of men killed, they planned on a daily advance of a few hundred yards with their artillery doing the fighting and the infantry moving up to occupy the terrain. This doesn't sound very daring but over a month, it would lead to substantial advances (certainly in WWI terms). And the French army was ideally suited to fight such a war, with excellent equipment and even more tanks than the Germans. It is a fallacy to think the French invested all their money in fixed defenses while the more modern Germans built tanks. The French had more tanks and as many aircraft as the Germans! This doctrine also did not require responsive communications or up front leadership. While the Germans pioneered the "general in the lead in his radio APC", the French still used the chateau general as that was adequate to their perceived needs.
This doctrine actually worked on the few occasions it was used properly. But the French were not trained to be flexible and after the Germans smashed through reserve divisions at Sedan, they were unable to regroup because the pace of the German advance was beyond anything previously encountered. And that's not just a French failing. The British lost every engagement until late 1941 against the Germans, as did the Russians and every other nation that fought against the Germans until 1942.
So just retiring a few old generals isn't really going to change that much IMO. You need a more responsive French army (with much better communication systems) or at least a decent strategic reserve which could have retrieved the situation after Sedan or in the later battles.