If they do not make any adjustment to the team by introducing some new signings outside of the French League following the exit of Mbappe, trust me if I tell you that their highest achievement will be the French Lig 1 title next season. They should never nurse any ambition of getting close to the semi finals of the champions league like they did this last season. I am not saying that they do not have good players, just that the squad is not just competitive enough to face other tough European teams like Bayern Munic, Man City or Real Madrid. You should not forget that it is expected that Mbappe leaving will create a huge vacuum in the team which require an external person to fill.
Even with mbappe the highest the have gotten most times has been the french Ligue 1, so it's no new thing, infact it's even a good achievement if they are able to keep on with the dominance and winning of the french Ligue 1 in the absence of mbappe, because that will mean that they were able to still maintain their strength a d their dependency wasn't on mbappe. Hopefully they get to achieve such height.
Going away from the french league to get a player to replace mbappe will not guarantee they will do any better in other Leagues either, it's high time PSG start looking and thinking differently in another direction because I observe they keep doing same thing over again and still remains within the Ligue 1 and almost never getting beyond. I don't and wouldn't want to undermine the chances of getting a good and Young talent around the french league who could be of a great importance to PSG, mbappe was once a young and up coming before he got to this point of his career.
Looking deep into the league ore wherever it is they would want to a d start building a team, by removing their mindset from the fact that they must buy a star player in oder for them to succeed beyond the Ligue 1 , after all they have the financial capacity, just like Leverkusen, they can look inwards and work with what they have and it's possible they can build a very strong team at all levels from there, this has always been my opinion.