I haven't seen Galtier being a perfect coach, if you say he has to be able to control the ego of each of his players, it should be quite a long time since he was appointed he should be able to improve relations between players. But until now the fact is that Paris Saint Germain is still the same as before which is still struggling with the selfishness of its players, I even think it has turned to its supporters.
If there is still selfishness in the players, PSG will not be more advanced in every season except for just getting a trophy in Ligue 1. Even though a team as big as PSG deserves to get a bigger trophy than that and also deserves to be reckoned with by other teams in different competitions and I think one of the things why PSG didn't get the UCL trophy until now is because this is something they haven't missing in the PSG team itself which should be very obligatory to eliminate.
Whenever you have a team full of superstar players, you will have to try hard about having balance in your team because any player thinks he is the legend and he is the most important player in the team, for example in PSG they have a player like Messi and who will never accept a player like Mbappe.