Real Madrid and Barcelona have dominated La Liga for decades and have always been on even terms. This is why El Classico is one of the best rivalry matches in history, especially during the Messi-Ronaldo era. Actually, I really regret the situation that is happening at Barcelona because they are facing a financial crisis and this will reduce the rivalry between the two. Yes, Barcelona became champions in the previous two seasons and Real Madrid became champions last season. But for this season Real Madrid have signed a contract with Mbappe who will be their icon and I don't see barcelona doing the same. Yamal is a wonderkid but it seems like the two are in different positions and I haven't seen any rivalry between the two.
It seems to me that you attach too much importance to Mbappe’s transfer, he will definitely not become a symbol of Real Madrid, if only because they have Vinicius, who may be no worse than Mbappe, and at first probably will be even better. Mbappe will be just a forward, perhaps he will have a chance to become the top scorer in La Liga, but there are also doubts about this, because Bellingham and Vinicius are players who play a lot in attack, and score goals just as often, so I don’t expect that Mbappe can do much differ from them.