There are places are people don't seem to do anything. But it's hardly a France-only occurrence. There are only plenty of companies where you are expected to work hard and deliver results; again, hardly France-only.
I love it when some casual observations from a visitor become trusted source of generalisation for a whole country.
I have the exacts same experience as you working at a NYC insurance company (9 to 5 then go home).
I also know at lot of companies here (in France) where people work their asses off everyday.
Perhaps six hours is all they need to accomplish the task?
And France is known for make it hard for people to find jobs.
Productivity, in other words, is a measure of the value produced per hour worked.
If instead we look at the most often cited measure of value produced per resident, namely, GDP per capita, France is not doing better than Germany or the UK -- in either "nominal" GDP or GDP "purchasing power parity" according to the most recent World-Bank data.