Do you really think that the % of casualty rates is an indication of military prowess? Doesn’t the higher % reflect the ineffectiveness of French arms as opposed to the other? Utterly defeated armies in full retreat with the enemy hot on their heels most always suffer more casualties than armies that retreat in good order.
Look at the rate of British casualties in France for the same time period and you should see similar high rates of casualties.
Also, you mention poor leadership, which is something I agree with, but you mention it like single-minded French Generals and an uninspiring French officer corp were not French, which, of course, they were.