Mbappe has much more experience compared to these young players, but the problem is that Mbappe can not cope with the pressure that is put on him in Real Madrid, and from the fans and perhaps with the failures that he faces in the team. In Monaco and PSG he was a leader, in Real Madrid it seems that he does not have such a status and is unlikely to be able to get it, so he will have to go through all this, and this will determine whether he can become the leader of the attack of Real or not, so far Ancelotti believes in him.
I think the problem is not the pressure, but the problem is his new position at Real Madrid. He can't give his best performance because he is still struggling and has to adapt to what he plays at Real Madrid. His position has been filled by Vini and that makes him have to be in a new position which is not easy for him to play. He also said that he is more comfortable when playing in his original position and that is not what he is getting now. I will not blame Ancelotti because after all Ancelotti must also have thoughts about strategy, especially since the position filled by Vini is quite good.