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.
Barcelona had good players already all they needed was the right coach to manage the players properly and that is exactly what Hansi Flick did he managed the players properly and now the result are different from how they used to be but just a few good performances doesn’t guarantee a UCL trophy. I believe because they won against Bayern Munich is why you sound so confident that they could win, even if they eventually win it it will not be as easy as you think and winning just one match doesn’t guarantee winning the trophy. 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.
Madrid fan or not i agree with you on this, Barcelona have improved quite so well and they are competing well in all competitions but the champions league is not la liga and it is not so easy to win after just recently improving your performance. 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.