I think the methodology is fine and it certainly isn’t complex. It’s just difficult to start using it when the corporate culture isn’t able to adapt and change it’s structures, that’s the hard part. Also a topic in the book.

Scrum is "bottom up" and the scrum master doesn’t manage anyone or anything, they are there to serve the team and get rid of obstacles. The team is empowered. If there’s a "manager" for the team, that’s already a mistake. That role doesn’t exist in scrum.