Kroos leaving Real Madrid does left a very big void in the midfield for them, but with Modric still in the club, he can be able with other younger players cover up for that position. I have strong hope in Real Madrid and I don’t think they’ll feel much about his exit in the midfield. I am sure Mbaope will miss most of those good passes that Vini Jnr and Rodrigo have been receiving to convert to immediate goals for the team. Kroos is a very talented midfielder and he will be missed in that midfield and that doesn’t mean Real Madrid's performance will reduce or won’t play as before. The existing midfielders can assist Mbappe and it’s just left for him to convert most of them to goals which I believe he can.
Kroos was the most important player in Real Madrid's midfield. Not because he was so strong defensively, but because he controlled the game. It's easy to get a good defensive midfielder, Camavinga can do that too, but apart from Modric, no one can play like Kroos and that position definitely needs to be replaced. Perhaps Arda Güler can take over at some point, but I'm not sure. Real will still remain the strongest team in La Liga but they have to replace Kroos and Modric in order to stay with the best clubs internationally.