PSG will be back to their full form shortly after the World Cup ends.
PSG has no opponents in Ligue 1, even without having their main players they could be champions of Ligue 1, PSG's biggest problem is that they have made big investments and aim to win the Champions League, and their objective is not so easy to succeed, so they need to be much stronger than they already are to win the champions league and since Ligue 1 doesn't have strong opponents it makes it very difficult for them to get stronger
I agree with you that Paris Saint Germain have no equal in Ligue 1, the real competition for them is the Champions League. In fact, I can say they don't need to worry when they lose 1 or 2 players who have been a mainstay like Neymar for example. Because there are still other players who can cover the positions left behind if they do their Ligue 1 matches. I think the Champions League is their main target.