Apart from what you said, I think we also shouldn't directly say about a setback for the PSG team because that hasn't happened after Mbappe left for Real Madrid. Because PSG still has time to think in order not to experience a setback in its performance next season and apart from that, I also agree with what you said, PSG can still dominate Ligue 1 even though Mbappe is no longer in their squad next season.
Competition in Ligue 1 is not a problem that Enrique has to think about because however the squad they currently have is still better than rival teams even though Mbappe is no longer in their team, PSG is the only strong team in Ligue 1 so I think the season In the future, the Ligue 1 trophy will still be theirs, losing Mbappe will indeed leave a hole in their front line, but it looks like players like Dembele and Ramos will be able to cover the hole, apart from that, currently PSG is still looking for a new striker to replace Mbappe PSG in front line to next season and I think they will get him soon after the fantastic offer they made to sign the players.
However, I also hope that other teams can take the opportunity to move better in order to match PSG's strength in Ligue1 next season so that Ligue1 looks more competitive than last season.
If you hope that other teams can improve their squads next season, maybe that will happen, but to compete with PSG, I think it will be very impossible because of the big gap between PSG and their rivals so far, PSG will still dominate Ligue 1 and Enrique should focus more on improving their team to be able to compete in the Champions League next season, currently PSG main target is not the Ligue 1 trophy but the Champions League trophy has become their main priority at the moment.