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.
You are right because there is no specific fix for such problems. The way inter milan squad is currently structured, they would have to do a complete overhaul of their current squad. That alone would take years before a new project like that will start yielding any result.
Manchester city have that problem because over the years, they have lost several key players that played crucial roles in their achievements in recent years.
Good things take time to build. Imo, Inter needs to start the rebuilding process sooner rather than later.