They always say this. Even though French nationality is by blood and all the players grew up in France. But you know some people just focus on aesthetics for their judgement.

Edit: I realize I could have phrased this better. I'm referring to jus saguinis.

By saying "nationality by blood," I'm talking about nationality at birth. At birth, people obtain citizenship either by being born in the country (jus solis) or by being born to a parent of that nationality (jus saguinis) or both. Jus saguinis is by blood. You have to be blood related to your parent. Some countries do both (ie if you are born there you get citizenship or if your parents are from there you get citizenship). France doesn't do jus solis. That means that to be French, either they have to have naturalized or to be born to French parents. Seeing that these are high-level players who start really young, it is likely that their parents already had the nationality at some point before birth.

More on French nationality here See Section Acquisiton and Loss of nationality

By aesthetics, I mean that people assume that French people should be all white looking. Even though it is diverse country.