Mbappe is a great player and one of the best players in the world. Mbappe's chances of winning the Champions League title with PSG are slim. Despite dominating Ligue 1, PSG failed to perform well in the Champions League. This is the main reason why Mbappe left PSG.
I would have been happy if Mbappe had left PSG earlier in the season. He is leaving PSG as a free agent this season. PSG have paid huge sums for Mbappe every season. Paid high wages. But PSG team failed to earn money by selling Mbappe. And that's why many say Mbappe is a bit greedy, and he's not loyal to the club. But I think Mbappe's decision to leave PSG is the right one. And this is the right time to leave PSG.
Yes, if they want the Champions League title for the next few seasons, it will be difficult for PSG to make it happen.
PSG must completely overhaul the squad and coach and that will take time. Therefore, Mbappe should be sold, maybe he also wants to chase the Champions League trophy with another team. I also believe that PSG will not develop if Mbappe is still around because the club has given him so much power that other people can't do anything, including the coach.
Why will PSG change their coach? Luis Enrique is a very experienced coach. PSG are very lucky to have an experienced coach like Enrique. PSG will definitely want to do well in the Champions League next season. For this, the PSG team needs to increase the strength of the squad.
Luis Enrique's main task now is to find a suitable replacement for Mbappe. Without finding a suitable replacement for Mbappe, PSG will not be able to do well in the Champions League. However, we still don't know for sure which player Enrique wants to add to the squad to replace Mbappe. But I believe Luis Enrique can make the PSG team more stable next season.