Generations will continue to change, previously Real Madrid also had great midfielders such as Zidane, Lassana Diarra, Luis Figo, Xabi Alonso and several other great midfielders. Their departure certainly left a big hole in the team, but Real Madrid has always been able to move on from them. Maybe at this time there is no one who can replace Toni Kroos, but the current stock of midfielders is still reliable. They just need to hone their ability to control the rhythm of the game and become creators in the process of scoring goals.
As generations passed so are change true and no matter how highly a player performs is either it will get to a point were they we sell him of transfer, players are not ment to stick to one club entirely and all the players mentioned are legends that there presence have highly affected Madrid then and now there young once coming up feeling there own space, and that is how it is suppose to be there should be continuation not just sticking to only one player always and if a player is good and leaves the club it will definitely affect the club, only in few circumstances that the new player will fit in better.
Toni Kronos is the real deal but they just have to continue with him, and Madrid is coming up gradually because Barcelona is just one point away from them now and it seems impossible at that time but there might even be a flip very soon, because Barcelona is already losing points so there position is no at stake because any fuck up they are dropping.