Barcelona's performance under Hansi Flick is indeed extraordinary, the coach did not need much time in his first season, he immediately managed the team very well as he has shown now, and indeed there is no need to doubt that Barcelona is a strong candidate team to win the UCL title, they only need to maintain their level of consistency in this increasingly tight schedule.
As a Madrid fan, I doubt Barcelona can win the UCL title this season. 
I admit that Barcelona performance is better now after replacing the new coach and in the end Hansi Flick proved that he is very suitable to be Barcelona coach even though he was initially doubted. But no matter how strong Barcelona is now, I am sure it will not be easy to get through all these challenges because there is still Liverpool who is much more consistent and has better quality players.
We saw how things went for Bayern Leverkusen and Liverpool last season, they were like the favourite for the Europa League title but sadly fell off to Atalanta in the Europa League, who came out champions. Though Barcelona is obviously not a small team and have much histories than the likes of Liverpool and Bayern Leverkusen but to be honest this is not the first time they have been dominating even in their domestic league and still fails to win the Champions League.