But not impossible of course. Every year there are new surprisingly good talents coming out. Mbappe was also found like that in the end. PSG scouts had better work hard by thinking of the possibility that Mbappe leaves this summer. Because from now on it seems quite possible.
And to be fair we are talking about a situation where it's quite clear that PSG already got much much better compared to last season, I have said this at the start of the season but their improvement on midfield is insane right now, which we can see even with their UCL situation.
That is an interesting point of view and I think in many cases I would agree with you that replacing a player doesn't always mean replacing that single player 1:1, but to make up for that gap that gap through collective effort and nearby positions. But I still think that there a few players around the globe that do leave a gap when they leave a club. There is just no way to replace a few of the top stars because their unique quality actually makes them who they are. Mbappe's explosiveness and dribblings can't be replaced 1:1 at the moment. As I said before, if we were to assume that any player is available at any time, then yes maybe you could say Vinicius Junior could get pretty close, but that's not reality. Hence, Mbappe, once he will have left the club, will leave a gap and the team will be weaker unless they can change three other players and make all of those positions 10% better. Mathematically, it could make sense overall, but it's unlikely that PSG can purchase a hand full of world stars in their prime.