The current bad reputation of the French is mostly because of WW2. They surrendered after only 6 weeks of fighting and then heavily collaborated with the Nazis. French collaboration was so heartfelt that they refused to hand over their navy to the British when requested to do so. They even fired on American ships and troops in North Africa when the Americans arrived to liberate them from German occupation.

The French were also enthusiastic participants in the Final Solution. According to Wikipedia, "the Nazis in France relied to a considerable extent on the co-operation of local authorities to carry out what they called the Final Solution. The government of Vichy France and the French police organized and implemented the roundups of Jews."

After the war, De Gaulle promoted the narrative that the French heroically resisted the Nazis, but this was not at all true. The famous French Resistance was tiny until the last part of the war, and only grew once it became clear that Germany would lose. The French government also denied their role in the Holocaust for over 50 years until 1995 when Jacques Chirac finally admitted that, "[T]hose black hours soiled our history forever. ... [T]he criminal madness of the occupier was assisted by the French people, by the French State. ... France, that day, committed the irreparable."

So, yeah, that's why people dunk on France, particularly when it comes to military matters. They certainly did not live up to the ideals of the Revolution or the martial prowess of Napoleon.