I don't think this is entirely Tuchel's fault. In previous seasons, Munich had also lost several times in the Bundesliga. But because other teams played worse, Munich could become league champions. This season Munich has 7 defeats and last season they had 5 defeats. That's not a big difference. You can see that Munich's achievements this season are not much different from last season. But Leverkusen's extraordinary performance managed to beat Munich and make them lose the title for the first time in many years. Yes this is Tuchel's fault but I think it is the fault of the team as a whole.
Yes Thomas Tuchel is not entirely to blame for Bayern Munich problems. Team up and down performance is shared issue and they lost seven games this season which is not much different from last season five losses. What made difference was Leverkusen great form which allowed them to take advantage of Munich weaknesses and win title. It is team effort and players need to take responsibility for their poor performance too. Tuchel decisions might have contributed to the struggles but it is too easy to blame only him. Whole team needs to think about what went wrong and improve to become the best in the Bundesliga again.
Of course, all team players need to accept responsibility and question where they made mistakes. Because Bayern Munich is a team that has become a school in world football. He has great prestige. If a team is considered unsuccessful if it does not win the championship, it is a great team and Bayern struggled with this problem this year. In general, what they have to do is to investigate where they made mistakes and correct those mistakes for the sake of the future.