I teach Aviation English to French ATC and Pilots and am amazed at the high level of English which they achieve - much better than my French! They certainly achieve true ICAO level 4 and 5 and some even 6.
Nobody would disagree that everybody speaking the same language on the frequency would improve situational awareness, however ICAO recomendations allow the French (and Spanish and Italian and Russian and Chinese ....) to use their own language so just get over it.
While we are at it, the English mother tongue ATC and Pilots could make an effort to use their own language correctly using an accent which is intelligable to the aviation community and giving a thought to the tremendous effort it takes for a non-native speaker to achieve even level 4.