Ligue 1 teams are quite weak compared to PSG. So Luis Enrique need not worry about winning the Ligue 1 title. Winning the Ligue 1 title is not a difficult task for PSG. So next season Luis Enrique will build his squad with the aim of winning the Champions League title.
PSG need a suitable replacement for Mbappe. It is still uncertain which player Luis Enrique will add to the squad as Mbappe's replacement. But OSimhen or Vlahovic could be a worthy replacement for Mbappe. These two players have the ability to score a lot of goals.
There is no doubt for PSG if they can continue to dominate Ligue 1 even though even without Mbappe later, PSG is the only team in Ligue 1 that has continued to dominate so far and even with the financial strength they currently have it seems that it will be very difficult for other teams to match or surpass PSG's achievements so far, so indeed when the current big project that continues to be built by PSG every season is not targeting Ligue 1 but indeed the league Champions became their goal.
What you say is true because so far PSG have always failed to get the champions league trophy and their curiosity continues to be a trigger for PSG to spend a lot of money every season, PSG's hope to win the champions league is certainly very big and even they do not hesitate to sign and pay a high price for the star players they are interested in, now Mbappe has entered his last season with PSG and their hope mbappe will be able to lead PSG to win the champions league, Speaking of Mbappe's replacement next season it is certainly not difficult for PSG to buy anyone at any price if he is considered worthy of being a mainstay next season.
The financial situation of PSG is what makes them different from other clubs of Ligue 1. The difference is honestly too much, even more than Bundesliga. Bayern has dominated the Bundesliga for a long period of time, but the competition gap has not been this much. I don't think Mbappe's leave would stop them from winning the league, but it would definitely be tougher to win it.
However, PSG has already said that they would sign 3 new promising players. If Enrique does his thing and creates team cohesion with his new team, I don't think there would be a problem for winning the league. But winning the league has become so common for them that it does not feel like an achievement anymore. They have struggled to win the Champions League even with their prime team so I think the focus should always be on that for a team like PSG.