Mbappe does not need to prove himself. Because he has proven himself in many matches he has played before. I don't think Mbappe is as happy as he used to be in the French league. PSG has not strengthened its squad like other big teams and the entire burden falls on Mbappe's shoulders. This is something a football player wants, but not every match can handle it.
I think Mbappe's adventure with PSG should end now.
When you say about a player who is 25 years old that he does not need to prove himself, what is he still playing for? Guys like Ronaldo and Messi proved it to themselves every single season for over a decade, many years more than a decade. Messi proved to himself and to the world that he can be a World Cup winner. I agree that there is no obligation to prove anything, but Mbappe is 25 and he should not play his whole career in a mediocre league like Ligue 1. He is such a great player and everyone wants to see him in the Premier League or Real Madrid. Look at Bellingham, everything he did was perfectly well considered.