Ronaldinho also played in the French league - also for PSG. And for Barcelona as well. So the only European team he played for that Neymar hasn't was AC Milan, and that was after he'd started his decline.
I think 'playing in the French league' gets used as a weapon to batter Neymar with just because many don't like him and are looking for something to undermine his impressive stats at both club, CL, and international level. It's not said about the likes of Thiago Silva, Verratti, Mbappe, Ronaldinho, Cavani, Ibrahimovic, etc, to question their motives or ability.