Madrid don't have bad players at the moment, but perhaps Mbappe could improve their game... Although I agree that they won't spend a lot of money on Mbappe... After all Real Madrid is a Royal club where any player would want to play, so they make the rules, not the player chooses to play for them...
Overall, there are no bad players in Madrid, in the sense that it is impossible for a club as big as Real Madrid to buy players of normal quality. I think, Madrid in the transfer market is also actively hunting for new players to build a squad for next season, after the departure of several players such as Benzema, Hazard, Asensio and Mariano Diaz. For Mbappe, it seems that Ancelotti is not interested in recruiting him, even though he has often been linked with Madrid a few seasons ago. It seems that the very expensive price and the complicated negotiation process made El Real's management discourage it from landing Mbappe in Madrid.
I think they were genius not to sign him, because Madrid could have used their money to sign two or three other players instead of signing Mbappe alone. Indeed, in terms of quality, Mbappe was very good when he was with PSG, but that is not necessarily a guarantee if he plays for Madrid. We can see Eden Hazard, who was bought from Chelsea at a high price but failed to adapt and ultimately did not live up to expectations when he was with Madrid.