Real Madrid is a team with a very large player pool. Kroos' departure will not have a shaking effect on the team. I'm sure Ancelotti has many alternatives in mind instead of Kroos. Kroos moved away from football at a somewhat early age. I think he could have played top-level football for 2 more years. Still, it's his choice and we should respect it. Real Madrid needs a quality midfielder for now. Let's see who will do this next year.
Actually, Carlo Anceloti has several options to replace Toni Kroos, one of which is by recruiting players who have the ability to regulate the tempo of the game like Toni Kross does, but the names that are linked seem difficult to get because their club owners are reluctant to sell them, but Carlo Anceloti doesn't just give up Real Madrid has quality players so they can use existing players like Eduardo Camavinga and Aurelien Tchouameni Carlo Anceloti is not at a loss he is so clever in arranging strategies we can see how Anceloti faces the season without pure stickers so next season there won't be a problem great even though the players are not as good as Toni Kroos but Carlo Anceloti will make the players look impressive next season with a little polish, just see 
Experienced and talented players like Luka Modrich and Toni Kroos are very difficult to find. Moreover, these two players can change the entire scenario of the match even in the last minute of the match. So I think it is not possible to find a suitable replacement for Modrich or Kross so quickly.
But Ancelotti won't face too many problems without Kross and Modrich. Because Ancelotti has been able to find several talented young players. And if these players can be looked after properly, they can perform better than Kross and Modrich in the future. Bellingham, Camvinga and Tchouameni are all very talented players.