Modric is old, but he is still playing like a young player because he is still doing well. This is good news for real Madrid fans because they have already missed Kroos, and it is better that Modric renews his one-year contract. I am sure that even after the season ends, they will want him to renew again. if he continues to do well. Real Madrid is completely prepared to perform well next season, even without Mbappe, and they are ready to compete with any club. Modric is not concerned about salary because if it were, he would have left Real Madrid and moved to the Saudi league, where he would have earned a lot of money. Real Madrid's first and second elevens are both good, and they are all fit. Real Madrid is expected to win the La Liga and possibly the Champions League next season due to their excellent players and ability to fight with other clubs.
Modric is old but golden but his decision to stay isn't a call from Real Madrid, the stay was his idea entirely. There talk about him been given a role as an assistant coach but I don't know how that went, maybe it was a rumor but he should be resting if I were him or better still go to where other old players are getting their retirement check in Sauidi Arabia and the retire from there unless he want to remain legend to Real Madrid but doesn't that even matter? I don't think so.
It will be dumb for Real Madrid to keep Modric as a replacement for Kroos, he is irreplaceable, his ways of changing the midfield games is different from the way Modric plays. If they are keeping him to enable young ones blend well in the game, then it's fine but Modric as Kroos replacement is misplaced priority and I don't see any reason for another extension of his contract.