Regarding the positions of Vini and Mbappe, it is indeed a difficult thing because both are good players but the problem is that they operate in the same position, which means that one of the players must be sacrificed to be rotated and occupy another position. And coincidentally the position needed is a center forward and Mbappe was shifted to center forward and the results have not been very satisfactory. He tried to experiment, but so far what he did has not been very successful. Actually I don't agree if the coach experiments in the middle of the competition, but I can understand that there are not many options for Ancelotti so he has to dare to make decisions, which currently do not look impressive, even tend to be disappointing.
I think if Kross didn't leave the team, Real Madrid would be strong as before, Mbappe will score many goals and people will see Real Madrid as a dream team.
Ancelotti already tried to rotate the players and use different strategies, but he hadn't find the best lineup. There's no more he can do except sign new players, either to boost the current players to play better or get the best lineup.