As a French guy I can tell you what our history books say ...
In both wars, the French military leaders and commanders behaved like retards, with a few exceptions like Clemenceau. What happened in WW1 is that they tried to fight it as if they were still in 1840's (as they had been taught in military schools, btw), underestimating artillery, and obviously machineguns and the few armored vehicles that already existed. The reason why France lost so many troops -actually mostly civilians with rather poor training at that time, France had basically no professional army apart from some specialized duties like supplies, drivers, pilots, and of course officers and generals- is kind of an "Agincourt syndrome" : seeing that this was not going anywhere, they went through quite a few suicidal assaults, gaining 300 metres each time if they were lucky, while losing thousands of men. Needless to say, it was pretty much in vain, and they were soon forced to wait for their allies' reinforcements.
Overall, everything in the French military was obsolete in WW1 :
equipment (in the first months of the war, some French soldiers still had their old bright red and blue uniforms, with fancy caps instead of helmets),
strategy ("No way the Germans would go through Belgium, it would take AGES !"),
training (soldiers weren't prepared at all to fight under heavy artillery fire, much less to a trench war),
supplying and transports (when they had to rush to defend Paris when they realized the Germans were almost at Paris' doors, they used horses, civilian cars borrowed from the population, cycles, and trains. There were close to no military vehicle),
even people's state of mind was from the previous century (soldiers were told they would be back for the next christmas ... Olol).
All this explains why, while eager to fight because of the rising nationalism of that time and having more money and soldiers, France failed to fight back efficiently. It's pretty obvious the whole French society (as blaming it all on the generals seems a bit too easy) was obsessed with the French Empire's military successes, and failed to adapt to the 20th century during WW1.
The same can be said about WW2 to some extent, but it's much, much more complex as there are a lot of political and social reasons I won't explain here because I can't be assed to look for sources
I can still look it up if you're interested though, my books are probably lying somewhere. Let's just say morale was horrible, and a lot of French people thought the republic was deemed to disappear soon anyway, so they didn't see any point in fighting.
Oh and huh ... You know the French "ability" to speak other languages, right ?
Sorry if my English is funky here and there.