It is not an easy thing to be able to compete in the Champions League, because in the Champions League the big teams compete, for Leverkusen of course they will compete with other big teams and maybe this will make it difficult for them, it is very unlikely that Leverkusen can immediately dominate the League Champions.
Bayern Leverkusen cannot just come in their first season in the champions league after so many years to dominate and win the game. They need to exert some kind of force that will not be stopped by any other team. They are the best in the Bundesliga and that doesn’t mean they’ll be the best in the champions league also. There are level to this, and I don’t think they can be able to win it straight up or even get past the semifinals if at all they’re able to make it that far in the competition.
Xabi Alonso is a great coach in the Bundesliga and Europa League, but for the biggest competition being the champions league, they’re never the ones to that will dominate it so soon. They need to show that consistency and keep coming back yearly to get a good grasp of the whole competition. Just after that, they can now confidently fight for the competition’s trophy in the coming years.
I'm certainly not underestimating the success of Bayer Leverkusen. 51 game unbeaten streak and undefeated championship title are not easy achievements. But if we consider that their toughest and most serious opponent this season is Bayern Munich and Bayern's poor form this season, Leverkusen's success does not seem like a dream achievement. Because Bayern Munich were really bad this season. They even finished third in the league behind Stuttgart.
Leverkusen couldn't dominate in the league against important opponents. In the Uefa Europa League, they made it out of the easiest group of the tournament with 6/6. In the last 16 round, they eliminated their rival Karabakh with a goal after the 90th minute. They eliminated their closest rivals West Ham in the quarterfinals and Roma in the semifinals with difficulty. They made it to the final without a loss and lost to their first serious and formidable opponent Atalanta in the final. A brisk and disciplined Gasperini Atalanta extinguished Leverkusen's dreams. Leverkusen were complacent throughout the season and they hit the first big rock very heavily. This deceptive success made them complacent. I don't think they will have a successful season in the Champions League.