One of the reasons why clubs like Chelsea is currently struggling as is because of the kind of players that they have signed in the past and that includes signing of players that are still in their teenage or developmental stages of their career as these players can't be used in challenging for a trophy because they don't have the mindset and stamina to do that what Chelsea needs currently are world class players that are ready made and can challenge for the league and help Chelsea finish in a good place in the league
If Chelsea are still signing young players it shows that they have not still learned from their past mistakes and history will likely repeat it self as they will struggle because these players can't produce results that will really put the club in a position that will be helpful to the betterment of the club
Honestly a mixture of world class together with the young ones wouldn’t be bad at all because these young ones seem to lack that elite level experience which they need to develop to the next level. Chelsea have enough young players in their squad already and should try a little mix up with experienced players to elevate them to the next level.