Barcelona shouldn't be in the list because they're struggling to fit into the system of balance. Pep Guardiola is my own favorite coach, he's important and makes football enjoyable because he's always on the top followed by Real Madrid. A club's level is determined by the performance exhibited by the club and their players. Manchester City remained first because their key players have returned to training, remember Kelvin De Bruyne is back and have scored and aissts for his team unlike some players that have no contribution to the growth of their club.
A very different performance can be shown by Barcelona in their next UCL fixture as that's the spirit that comes with UCl so it won't be fair enough to just rule them out because of some sense of struggle around Barcelona after all they have been winning their games in their domestic league recently so they could be on the track of improvement without you knowing.
Until the round of sixteen is over I wouldn't be ruling out any team not minding their strength because I know for sure how much most teams would wan to participate in an elite league such as the UCL and a chance to have gotten to the round of sixteen isn't on they will make a joke with so they are definitely going to put in that required efforts such that underestimating any of them maybe to your own detriment so even the bigger team should be wear too lest they loose embarrassingly to a side they would consider weak.