I think if Kross didn't leave yet, Real Madrid would be strong like 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.
Until now, no one has been able to replace the quality of Toni Kroos at Real Madrid. As a player who was named the world's best playmaker in 2014, he is indeed one of the star players who is difficult to replace. He plays an important role at Real Madrid and losing Toni Kroos also seems to have its own impact on this team. It is truly a shame that Kroos chose to retire at an age when he is actually not old. But he made that decision because he wanted to retire at the peak of his career. And yes, he reached the top last season with Real Madrid because he won LaLiga and UCL at the same time.
I agree that Ancelotti should also start looking for potential and good players who can add strength to Real Madrid, especially in the midfield and back line. because we see that even Real Madrid's second tier players are currently not capable enough to replace the main players there. Because there is a very clear difference in quality between the main and reserve players.