Chelsea have seen steady improvement since Maresca's arrival, and their success in winning the Club World Cup should be a good indicator that they can do the same in next season's Champions League.
You're right, as you said, Chelsea shouldn't be underestimated. Personally, I'm quite confident in Chelsea, and they deserve to be placed among the favorites to win next season's Champions League. If that happens, it wouldn't be a surprise, as Chelsea have a pretty strong squad right now.
Since Maresca took the head position at Chelsea, it has been a progressive growth, one that has been consistently reviving the team in almost every area where in they were dieing off, I love it that now they have a trophy that has added to boosting their confidence enough for them to even do better in this new season at the premier and champions league but I do not trust them enough to win the champions league but may possibly attempt the premier league and finish decently.
Indeed Chelsea have made a lot of improvement in their performance, and honestly they are looking so good in terms of performance. Right now this season they can win something good like Premier League titles, etc. but honestly if we talked about the UEFA Champions League titles, then apprantly it would be hard to speculation that who will be the winner because this season there are many other team who are in intense push to grab the UEFA Champions League titles. Such as Barcelona, Real Madrid, PSG etc.... and I don't think that Chelsea would be good enough to play against them or defeat them.
The rest of Chelsea is a good team. After the arrival of Maresca, Chelsea has lost its poor quality and adopted a better version which can definitely increase their chance for league titles winner....