PSG have much better squad depth so losing Mbappe to injury will not affect their overall performance too much. Unlike other teams, if one of their important players is injured it will affect their performance. That's why squad depth is very important because the competition lasts a long time and losing some important players will affect the results because the coach has no choice to rotate some players in those positions when they are injured.
If Mbappe is injured, that means Enrique must have a way to maximize his squad. that is why, a football club needs a coach. We know and understand very well that Mbappe's contribution to SPG is very large. However, I think Luis Enrique has prepared various tactics and strategies, if the time comes when his main players are injured. The point is, that football is a game of teamwork. For now, Enrique is prioritizing Mbappe. However, when he was injured or left, Enrique had to implement other options and plans. After all, PSG has a better squad than its competitors in Ligue 1. However, it seems they need time to reach their level of play. On the other hand, when Mbappe was injured, Enrique had to be able to maximize his players without any stars. That means teamwork is really relied on. and on some points, I agree with what you say.
Nice has shown a good performance to date and places them as one of the strong contenders for the championship. But the problem is as we discussed above and consistency will be a big problem for Nice in maintaining their position in the standings, especially since the difference in points in the standings is not too far from their challengers.
As for Nice, to be honest I never know which players are really their mainstay. That doesn't mean I underestimate Nice. It's just how long this team will be able to maintain its ranking at the top of the standings. We can refer to statistics from the 11 matches they played. 7 wins, 4 draws, and never lost. However, they are very minimal in terms of scoring goals. So far, they have only been able to score 13 goals. different from other teams, which are quite productive. I will just say, gradually Nice's position will be overtaken by teams below their ranking.