No I disagree with you, Barcelona relying on their current players will give them more advantage to advance further in other competitions they will be involved in next season, they will not be needing time to study their performance and all the players were involved in their brilliant performance last season they will equally do better next season once they are free from injuries and suspension. As for Barcelona making it to the champions League semi finals next season, we can not predict ho it will happen but if they are as strong as they are in the just concluded season then I think they can even get to the finals then win the champions League next season.
Barcelona does not need to change their squad. Lewandowski was Barcelona's top scorer this season. Lewandowski's fitness is good enough. He will be able to perform well next season as well. Also, the young Raphinha and Yamal are gradually becoming experienced. It can be expected that we will see better performance from these two players next season.
Barcelona's attack and midfield are strong. If changes are made here, the performance of the players is likely to be a bit unstable. However, Barcelona's defense needs to be strengthened. We have seen Barcelona's defenders perform badly in several important matches this season. So Hansi FLick may try to strengthen Barcelona's defense. Barcelona will want to dominate both the Champions League and La Liga