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.
Toni Kroos departure will not have much of an impact on Real Madrid performance, Ancelotti still has other players who can replace his role in midfield. It is not too difficult for a team like Real Madrid to find a suitable replacement to replace Kroos, especially now that they have Bellingham who has excellent goal scoring abilities.
Kroos decision was very surprising because he is still able to play at a high level and his abilities are still very stable, but he chose to rest sooner than expected. Real Madrid must prepare an ideal replacement because soon they will be left behind by Modric.
I really agree with Toni Kroos leaving Real Madrid, but Real Madrid still has Luka Modrić, even though he is no longer young, his game is still capable of providing good passes to players, not only Bellingham but Mbappe is also new ammunition for Ancelotti's squad, according to I think Ancelotti would be better off waiting for the upcoming transfer market rather than looking for a player for now, because he can use the existing players to give playing minutes to the central player who can be a replacement for Toni Kroos.
If there are no changes during the middle of next season then Ancelotti must quickly find a replacement for Toni Kroos to cover existing weaknesses when needed, but if not then the first option of using young players is a good step for the Real Madrid academy in the future.