Ten Hag have had experience in this league before so there's chances that he could do well, I'm not going to conclude until I see how Leverkusen would perform in their first 5-10 games until then Dortmund are the only team I feel can challenge Bayern Munich even though I doubt if any team would take away their dominance like Leverkusen did when Alonso was there. Well with the squad Xabi left for Ten Hag getting into the Champions league shouldn't be a big deal.
Bayern Leverkusen squad are not that bad even though some of them have been sold out to other teams for the continuity of their careers there. They were still able to finish as runner up last season when Xabi Alonso was still in control of the team, this shouldn’t be an issue for Ten Hag to make that qualification every season because he has the squad that should be able to pull that through for him under his good management. I don’t doubt Ten Hag capacity even though he happens to not finish the season well at Manchester United when he last managed them and was sacked. This is a different club, different league and a different challenge, he should also develop here with time and could be at his best here than he was at Manchester United.
They are definitely weak in the efforts of some team, which reduces their strength. If these players played thinking about the development of their team, then it would have been beneficial for them and also for the strength of their team, which they have damaged. But the real reason is Leverkusen, which is not a good squad for them, if they improve themselves, it will be good. They are a good team, that is why they are most likely to succeed. If they also play with full effort, they will be completely successful in their goal, which will be a very good effort and strength for them. This will also happen only when they do not work hard and go above Manchester United and do not play with too much struggle. If they succeed in this, then there is a danger for Manchester United.