~Snip~
I have a slightly different opinion than you on this. Even after Mbappe leaves, Paris Saint Germain will continue to win the French Ligue 1. But I don't think they will be able to find a replacement for Mbappe. Messi, Ronaldo, and Mbappe are special footballers. Paris Saint Germain, Barcelona, and Real Madrid will continue to win titles. But they need to sign players who are at least as good as them to recapture the glory of their playing days. Bellingham fits that description. That's why Real Madrid had a good season. But we can't say the same for Barcelona. Paris Saint Germain are very lucky to be in a league with weak competition. They will continue to win the French Ligue 1 even without Mbappe.
PSG cannot remain silent with the absence of a quality striker after Mbappe left, they must move aggressively to find a suitable replacement to maintain their sharpness on the front lines. It is very difficult to find players who are equal to Mbappe, but PSG must choose players who have a bright future to make it easier for them to win trophies.
The UCL trophy is still the only one that PSG has never won, without quality players it will make it even more difficult for PSG to compete with other elite clubs. Being in Ligue 1 gives it the advantage of being able to win domestic trophies easily, but due to the very low competition in Ligue 1 making it difficult for PSG to compete in the Champions League. PSG must take advantage of the opportunity when the transfer market opens, they can buy any player they deem suitable to be included in their squad because they have so much money.