Yes, Chelsea was the team who stopped PSG from winning the tournament, but they also lost to Botafogo in the group stage, despite some people believed that it was a fixed game, PSG they knew would not lose if the match was important to them. PSG may still win the Champions League back to back with the previous squad, but it seems that they still want to strengthen their squad after the defeat against Chelsea, as they just signed two new players.
However, Luis Enrique understands how to manage his club, and I'm sure they will need more players for the upcoming season. After the pressure of last season, most of their important players may not be at the same level since they need more time to relax and return to their best form. Chelsea is another team that we cannot write off in the Champions League this season, I believe they have the strength to win it.
Chelsea still have to prove how good they can be in the Champions League, despite the fact that they won the Club World Cup, no one took this tournament seriously, perhaps with the exception of the last playoff games, but the tournament still remains not very status. The Conference League, which Chelsea won, is also a low-status tournament and Chelsea had to win it, so in order for them to start being taken seriously, they need to play well in the Champions League, but for now it is too early to talk about their strength.
Seriously, no one takes the competition seriously. Even Real Madrid was willing to spend 10 million euros to bring TAA in early and take him to the FIFA Club World Cup, even though if they had waited a month, they could have gotten him for free. Likewise, Manchester City tried to strengthen their squad ahead of the Club World Cup, such as by signing Tijjani Reinders from AC Milan. Those who think this isn't a serious competition are those who haven't seen their favorite teams compete in this competition or are eliminated and fail to win the title.
And back to this season's Champions League, they may not be the favorites to win the trophy, but surprises always come from London, especially when it comes to the 2020/21 Champions League. They were the team that managed to stop Manchester City when they were in their prime. So I have absolutely no doubts when Chelsea returns to play in the Champions League this season.