Juventus must recruit several players for next season because the strength they currently have is not strong enough to compete. Building a team with much younger players will make it easier for coaches in the long term so they can adapt and be solid every time they play. Juventus' current strength is not very strong and they have to replace several players who are already old.
One of the reasons may be that he has experienced players but there is no guarantee that he will be able to compete for the title. Just like what happened last season where they were unable to face several crucial lags by relying on several experienced players because they were inferior in quality to the opposing players.
Juventus still have a lot to work on their team because right now they are not on their best performance and it was even with struggling they were able to secure the third position they did on this season making them to qualify for the champions League next season, so perhaps if is a club that needs to improve next season they will never hesitate to recruit more capable players because last season may likely be nothing compared to what they will see next season, so preparing ahead of time will be actually a great beneficial to them so that before the next season they will be ready.
Yeah for now especially with their performance this season I don't think they will be a threat to other team next season because they don't have what it takes now, however is very obvious that they will find it difficult to cope on the champions League because their are so many clubs there that's doing very well more than Juventus so if they failed to invest on more players I'm afraid they may not even be able to qualify from their group stage.
Since the beginning of this season, Juventus has been consistently winning their matches in the Serie A and competing with Inter Milan for the Scudetto. But after Inter Milan beat Juventus for the Scudetto, Juventus started struggling to win their matches in the league, and they even found it difficult to qualify for the next season's UEFA Champions League competition. If Juventus wants to challenge Inter Milan for the Scudetto next season, they need to overhaul their squad so that they can get good results when the new Serie A season starts. But if Juventus fails to do this, they will get a similar performance as they did this season when the new Serie A season starts because their squad is not good enough.