Mbappe has been with PSG's squad for a long time. And Mbappe is PSG's regular scorer. This is why Mbappe's departure will definitely have an impact on PSG's overall performance. There is no denying it. Last season Luis Enrique experimented a lot with the PSG squad, keeping Mbappe on the bench. PSG's performance was stable without Mbappe. However, PSG's overall performance was not strong.
Luis Enrique is an experienced coach which is why he started preparing the squad without Mbappe from the previous season. He will surely find a suitable strategy to keep PSG's performance stable. But I look forward to seeing which player Luis Enrique will add to his squad as Mbappe's replacement.
That is the talent right there, dude started to play the team without Mbappe even while Mbappe was there, and he took Mbappe out of games so frequently, it's basically a way of telling the team that they do not need Mbappe, and seems like it worked very well.
I think next season when they actually have a missing superstar, they are going to still be fine because Luiz Enrique is such a good manager that he instilled that notion on their minds even before Mbappe left. They will of course spend some good chunk of money to get some new players as well, they always do that so it wouldn't be a shock if they do it again, it would be quite good result in the end. It's hard to replace Mbappe, but it would not be impossible to get some good players.