PSG is a big team currently the best in Ligue 1 for years and are financially capable of getting any top players but what they need is a good coach like Pep Guardiola that would build a very strong squad and instill a winning mentality and probably lead them to victory in the Champions league which they're desperately in need of, as for players they brought in good players to replace the departed ones and so far they've been impressive in the Champions league and has to maintain that form to be able to succeed in the tournament.
Mbappe is the most reliable player for the team and is very important for them due to his goal scoring ability and they'll need him to be in form so as to help them try achieve the Champions league this season, but I feel Mbappe might seize to be a player of PSG by next season.
PSG have tried to sign Lionel Messi for two years but can't winning UEFA Champion League tittle, although having good financial and spent for active in window transfer still not guarantee for PSG winning Champion League tittles. In this season, PSG opening Champion League match with good result after winning from Dortmund but I don't think PSG is favorable teams become the winner in this season. Dominance in domestic league only is not enough for PSG how to be compete in Champion League, have possibility with opponent teams when 16th round not facing with big team like Bayern or Real Madrid and has chance for PSG will qualify until semifinal stage.
Last two season, Real Madrid and Bayern Munich are nightmare team made PSG can't qualify to quarter final and have stuck on 16th round phase, seems difference if both teams above not opponent teams for PSG in 16th round.