I agree with you. We all know Mbappe was the most important player in PSG's squad. There is no doubt that Mbappe was PSG's leading scorer. But I don't think PSG can dominate Ligue 1 without Mbappe. Without Mbappe, it may be difficult for PSG to perform well in the Champions League. However, it will not be difficult for PSG to dominate the league.
PSG is a very rich club. And they never skimp on spending money. Moreover, PSG coach Luis Enrique is very experienced. Luis Enrique will certainly take whatever steps are necessary to strengthen his squad. And Luis Enrique will get all financial support from PSG management. So I believe Luis Enrique will be able to keep the performance of PSG team stable in the next season as well. And PSG will dominate Ligue 1.
It should be so that Paris Saint Germain will not have too much difficulty returning to dominating the league, because they are the best team with a luxurious squad compared to other teams, so for me there is no reason for them not to dominate the league. In my opinion, Mbappe's departure cannot be a reason for them to lose their dominance in the league.
However, if we talk about the Champions League, then I agree that they will have difficulties as usual. With Mbappe in the squad they are still having difficulties, in fact they once had 3 star players at once and it didn't have any impact on them. Now they have to realize that star players alone are not enough to bring them success in the Champions League, so they have to have a winning mentality too, and that must be owned by the team as a whole, not just by individuals or just a few players.