Currently the main problem for Real Madrid is the selfishness. Xabi Alonso is also aware of it and wants to take immediate action about it. The board is fully supporting him in this.
Mbappe, Bellingham, Vinicius Junior... These are the first selfish names standing out in the squad now. If their attacking line learn to play as a team instead of an individual only, I believe in Real Madrid to be a superb team just like PSG now...
Bellingham is not part of the attacking line in 90% if the games and he is not a selfish player. Vinicius Junior and Mbappe are selfish players and that can become a problem for them because Real Madrid can't afford too many players that wait in the front and don't do their part to defend backwards.
When you compare this to Barcelona, all the players are willing to put in extra effort to help the team defend against the ball. Lewandowski, Yamal, Raphinha are all players you can find in their own half from time to time, trying to pick up the ball and change the momentum for their own good.
I never understood why Vinicius Junior was chosen as the best player in the world. In my opinion he never deserved to get that award and he isn't even top 3.