PSG were once very desperate to win the Champions League trophy, and now they have it, and I think that has definitely made their mentality even stronger, so I think they do have a chance to go back to back next season. It certainly won't be easy because the other big teams will definitely be making more thorough preparations (especially Real Madrid and Liverpool who are currently very active in the transfer market), but that doesn't mean PSG can't win it back because in football anything can happen.
They managed to win the title last season but it's not easy to form a mentality in the Champions League even though they have won it because before we tried to compare Real Madrid with PSG then I can say it's completely different. Real Madrid have been so dominant in the Champions League that comparing a club like PSG with them is completely irrelevant. PSG will definitely be better after winning the Champions League but defending the title for two seasons in a row is not easy and I believe next season will be much more competitive.
Real Madrid has built a strong foundation in any competition, including the Champions League, while PSG, they have just built that foundation, which now makes PSG one of the most respected clubs in European and world competitions.
This season PSG has succeeded in conquering Europe, so the next step is the club world cup competition, because they have a goal to become one of the best clubs in the world. For now, the player material owned by PSG is quite good and balanced, so I think at the end of this season they should also be able to conquer the 2025 FIFA club world cup.
PSG can't be compared to real Madrid just because PSG won last season champions League, let's not forget real Madrid has won a lot of champions League title, however PSG just like you said have just built that foundation in champions League and that is a very good achievement for them but they should keep this on, I'm sure next seasons champions League they will go far and may even get to the final, yes it won't be easy but is not impossible for them, they are inform all they need to do is to keep the form going.
PSG can win the FIFA club world cup, if they can win champions League title then is very much possible for them to win the club FIFA world cup, all they need to do is to keep this there form going, in yesterday's match with Atletico Madrid they won 4:0, I was not surprised with the score because PSG is very much inform.