It's not a matter whether the transfer window is still open or not, but suddenly changing the old midfielders with the new midfielders mostly will not work. It take time like 2-3 seasons to built up, the situation is similar like Real Madrid. Kroos, Modric and Casemiro were solid midfielders, but when Casemiro leaving and Modric get older, Tchouameni, Camavinga and Valverde are the next generation who will replace them.
Currently only Valverde is really performing in Real Madrid, Tchouameni and Camavinga are still struggling.
First and foremost, this topic belongs under the La Liga thread because it contains more information about Real Madrid. Perhaps that's not the point; Real Madrid has good players who can fill in for these key players stated above. Luka Modric and Toni Kroos are growing older by the years, and their time at the Santiago Bernabeu is drawing to an end. Concerning the future, Aurélien Tchouameni, Eduardo Camavinga, Federico Valverde, and Jude Bellingham are all talented players, with the main difficulty being their capacity to mature into displaying spectacular performances in all league games, they will develop, what they need is good buildup and time.