This is because inter Milan has refused to bring in younger players to strengthen their squad and this has impacted negatively on the and we saw that in the finals of the Euefa champions League finals were they were humiliated by PSG, inter Milan should start a rebuilding stage if they are to come back to competitive football challenging for titles.
It is not about getting younger players per say but rather getting the quality players needed to compete again. That aside I think their issues goes beyond getting new players they are underperforming and in a worse state than Manchester City facing similar issues although while new signings have help them they are still not in their best or usual performance.