Modric was 37 years old and real madrid is still offering him a new contract for another year. benzema potentially to get the same thing next season from real madrid as long as he is still showing impressive performance.
Modrid plays very well at this old age and he can run a lot, run quickly enough than other old players. I don't know how a tiny player like Modric can maintain his body to play aggressively at this age. I am not surprised if old players depend on their experience to play and avoid to waste their energy for running but Modric is different. He uses both his experience to play but also is very ready to join any physical fighting with younger players.
His ability and skills to make passes, do ball control and helps his team to have good ball possession as well as switching quickly from defense to attacking is simply massive. It is hardly to find in any player, any play-maker in football. He is a valuable player for Real Madrid and Croatia.
I think his pace is not what makes him different compared to other players. Most players at his age stop playing, and that is usually regarding physical situation, not many people keep in shape at that age, and some of them even retire and have a big belly by that age, so it is true that Modric took care of his body and he is still fast.
However, I also think that him adjusting to his new position and his physical situation better is the key point, many people will not remember his very young ages, he was playing at AMC spot, as in he was right behind the striker, or more like false 9 of today, like Firmino played for years, but usually he was right behind striker, nowadays? He plays right in front of the defense, because his pace there is much better, he is not fast enough to beat defenders, but he is fast enough to cover passing lanes as well.