At the age of 38, of course Luka Modrić is no longer able to compete in playing in the top European leagues, so it is only fitting that Luka Modrić spends the rest of his career playing in the Saudi Arabian league to collect more money and also there the league is not competitive making him Luka Modrić can still compete in showing his performance, which is different if he stays at Real Madrid.
Real Madrid only needs Luka Modrić to be able to guide young players so that there is regeneration in the Real Madrid team and he has been doing this for the last few seasons until now it is time for Luka Modrić to leave, either retiring or continuing his career in a non-competitive league. I think it's the same, those are two good options.
We have the top clubs in La Liga this season. Real Madrid have reach far this season, is regarded as the best team in La Liga this season, they have the best performance and doing the ultimate work to reach important phases this season. Carlo Ancelotti knows the high class players he have in his team and he's really comfortable working with them. Luka Modric is one of the top players in Real Madrid and he have earned his place in the team. He's currently referred to as Real Madrid legend based on his contribution to the team's progress over these years.
Real Madrid have been in the limelight of football for quite some time now and one of the biggest team in the world right now, if am not mistaken they should be the top number one team in the world, they have gotten so many records and has won a lot of trophies so they have already made name that will stand for a long time.
Luka Modric is getting old though he still gives in his best whenever he is being featured in a match so if he decides to move to Saudi Arabia league to make some cash before his retirement it will be a good idea