Tony Kroos can be an interesting search for Manchester City. You know he is still a great player, even though he is thinking about his retirement. And I believe he is definitely going to perform well even though he is not very young anymore. Yes, I also think that Manchester City will be able to use him properly.
Don't get me wrong, I am not saying Real Madrid is using him badly. If anything, Real Madrid is using him the best. But as he is already thinking about retirement, it will probably be a good journey for him to join Manchester City and achieve something with another club as well.
Manchester City will not invest money in players who are much older and I don't think Tony Kroos is suited to playing at Manchester City because their style of play relies on speed. Pep Guardiola has the opportunity to recruit much younger players because Manchester City has unlimited money, so choosing Tony Kroos is not a solution for their midfield and the English league competition is slightly different from La Liga so strength is needed.
Tony Kroos has played more on the bench this season because Ancelotti relies more on the strength of young players and if he is installed as a starter he will definitely be a tandem of young players and will not always be played together with Luka Modric. If he wants to leave maybe the Saudi Arabian league would be a good place before he decides to retire in my opinion.