The French front four look unsettled at the moment. That early Irish goal has shaken them up. They can't keep the ball and pass it around comfortably. It doesn't help them both Payet and Griezmann want to drift inside all the time. Neither player wants to be involved in a 1-on-1 and beat their man. There's no one there bar Pogba who's willing to stretch the Irish defence with their 1-on-1 battles. They need someone like Martial or Coman in there who can dribble their way out of trouble and face their markers rather than get away from them. The French being too central has made it easier for the Irish to defend against them, keeping things tight and compact.
Daryl Murphy and Shane Long have caused Koscielny and Rami a number of problems as well. Both have struggled to deal with their physicality and tenacity. Ireland need to keep directing the ball towards them in order to keep France under pressure.
For France to improve, they need to get some width in the team to stretch. Coman or Martial for Matuidi, Griezmann, or Giroud.