#2 Experience
In highly competitive tournaments such as the World Cup, experience matters a lot. In the game between Brazil and Switzerland, the Swiss were nowhere near Brazil's individual quality, but the players of that team had more experience playing together compared to Brazil, and they managed to hold Brazil to a 1-1 draw.
This French squad is relatively very young. The likes of Mbappe and Dembele can easily play for U21 as well. Apart from Hugo Loris, Griezmann is the most senior most member of the team at the age of 27.
Their team is clearly filled with young and energetic talent, but it lacks the experience of playing as a team. It is also the first World Cup for many of the players on the current roster.
Only Pogba, Griezmann, Loris, Varane, Matuidi and Giroud were the French players who played in the 2014 World Cup. Even if this squad is compared with France's Euro 2016 squad, then only 7 players are in the current roster.
Thus this team with all its talent has little experience playing together as a unit. The majority might have played big games for their club sides, but most of them have not done same for France.
As already stated, at big tournaments experience will play a crucial role and lack of it could hamper the chances of France to have a good run in this World Cup.