I don't believe Mbappe leaving PSG would make them not dominate the French league. They still have so much money more than every other team in the league. They still have to money to sign the best footballers in the world, other Ligue 1 teams don't have that luxury.
Without Mbappe, the coach just needs to build his team around other players. PSG have a good coach in Enrique and he knows how to manage a team.
I believe PSG would still win the league comfortably next season, and yeah I also believe without Mbappe, the recognition of the Ligue 1 would reduce a bit.
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.