Luis Enrique definitely has several options to find the best center forward to replace Mbappe next season. Randal Kolo Muani might be good for that position, while Goncalo Ramos is also good. I don't see much to think of as anything negative from PSG, they'll be fine I think.
There are still many players who can fill the void left by Mbappe, but the question is whether these players can do their job well or not? I think this is a question that almost everyone has when looking at the Paris Sait Germain front line that Mbappe has now left behind. This is because the expectations for the players who fill that position will be very high, because they will see Mbappe as a comparison. Although personally I don't really like comparing, some people do.
Luis Enrique is expected to be able to do his job well, especially when implementing strategies on the front lines or he must be smart if he wants to bring in new players. The reason is that this position is a very vulnerable position, because it is directly related to their goal productivity. The reason is that if they have difficulty scoring goals, then they are in big trouble.
It's one thing for Paris Saint Germaine to sign a world class attacker that'll serve as Kylian Mbappe's replacement at the club but absolutely a different thing for the person to become as effective as Kylian Mbappe have been at the club over the years. I don't think it'll be possible for the club to get a player that can be as prolific as Kylian Mbappe or have the same impact he used to have in the Paris Saint Germaine team. For the past six seasons, Kylian Mbappe haven't just finished as Paris Saint Germaine top scorer but also have been the top scorer in the French league in that same duration so getting a player that will register those same numbers of goals per season will not be possible for Paris Saint Germaine.
Without Kylian Mbappe at Paris Saint Germaine, I know it'll affect their performance however, I'm of the opinion that they'll still continue to dominate French football because even in the absence of Mbappe, Paris Saint Germaine team is the the strongest team in the French league.