PSG won the Champions League title last season and it seems that they are ready to fight next season with the same team they performed with last season but my question is will PSG be successful next season by competing with the team they competed with and succeeded with last season? The big teams could not do well last season for some reason but those teams will perform well next season which will make it difficult for PSG to win against those big teams with the current team they have. I think PSG does not need to change many players in the team but they should buy some players. If they recruit some players to their club then their team will be stronger next season than last season and in that case they will be able to compete against any team but it will be tough.
When a team successfully wins the UCL, it does not mean that they will be able to do the same thing next season. PSG is not necessarily able to beat the same team that they beat last season. If this were Ligue 1, I am sure PSG would be champions again. They are too dominant in Ligue 1. But it is different with the UCL where the contestants are elite European teams who certainly have great motivation to win the UCL. Many teams have made player purchases to cover their shortcomings in the previous season. And this is a sign for PSG that they will not face a team with the same composition of players as before. I don't know if buying new players is the right decision for PSG because for this season I think their squad is perfect in all aspects.
It is very rare for a team that is successful in the UCL league this season to win again in the next season. Because many factors occur, as you said, each team has made big changes and has a greater motivation to win the UCL league. And it also often happens, in the next season the team meets the previous team can win, but in the following season usually loses. I also always have faith, winning the title is difficult but defending the title especially in the champions league is much more difficult.
Moreover, the motivation of PSG players is no longer as enthusiastic as last season when playing in the UCL league because their dreams have been achieved. The motivation of each team in one season always changes and is different, believe it or not it always happens. Just look at PSG just lost to the Botafogo team in the club world cup.