You're right, if Mbappe goes to Real Madrid, the team will probably become much more dependent on him. But has Mbappe been experienced enough at the moment? That he will be able to take charge of the entire club? Big clubs like Real Madrid definitely need experienced players. Mbappe is a very talented and extraordinary player. But he still lacks experience. We have seen how he has performed for France in the Euros. Benjama has played much better than him.
Mbappe has already taken part in all tournaments that can be imagined and he has many achievements and titles (by the way, he is the world champion if you didn't know). He is ready to move to Real Madrid, and tell me, can Mbappe, being in PSG and the weak French championship, really progress and gain some new experience? I'm sure not.