Compare the ages of Modric and Cross, and you can imagine how many more seasons Cross can play in Real Madrid if he wants. Last season, Real Madrid did not have Bellingham, and in the new transfer window, Real Madrid can sign a contract with another talented player, this is not a problem when the club has money. Modric is technically a very talented player, this is what allows him to play at such a high level despite his age, but he will not be able to play at this level for a long time.
The talent and experience they both have in football history and in the league is why Real Madrid did not sell them, because if they had left the club, Madrid would not have been in the form they are now because they need players of that caliber to coach and guide the team to success.
But, in the eyes of Real Madrid fans, Jude Bellingham has been a successful addition due of his performance; if Madrid signs more players of his caliber in the middle, they can do without Kronos and Modric.
Real Madrid prioritizes Modric because of his talent and experience, he is the mainstay of Real Madrid midfield, but I agree with the fans who want a change in the midfield by recruiting another player of Bellingham caliber. Young people are needed because their stamina can be better rather than older players, and to be able to continue competing Real Madrid needs big change. Now with Bellingham, it makes easier for Real Madrid to recruit new players next season, because they have other mainstay players in midfield.