Only Real Madrid have been able to win the Champions League back to back. Apart from them no other club has done it. This is why I don't think that PSG can defend the title because they cannot be in the same form like last season. Many clubs have improved their performance by by additional players to strengthen the team. I believe that PSG will find it difficult to win some big teams that they defeated last season.
I would have loved to see a different club entirely winning the title this season.
That's the reason why Real Madrid strength is so taken into account when playing in the Champions League, they have complete attributes to compete with any team. However, it's not impossible for PSG to succeed in defending the trophy this season, and I wouldn't be surprised if they manage to do it. We understand that the dynamic of the competition for the trophy this season is very different from last season, but PSG hasn't changed much.
Meanwhile, it would certainly be delightful if a team that has never won the Champions League trophy before managed to do it this season, I think Arsenal is one of the teams that has the potential to do so.