Managers perform a helpful role. There’s a lot of ways to be bad at everything and many (most?) people are minimally effortful which exacerbates the actual difficulties. Good managers (in my experience) are uncommon but managers are common.
However, I am convinced that if a person’s title is Scrum Master it doesn’t matter how much effort they give for their job; they will never fix the error of their position being created and filled.
it 100% depends on the project and is demonstrably false for many things I participated in. For example, if you are a fintech integrating with a bank - which is very important for moving money cheaply and being able to make the ends meet - like 80% of the work is bullshit meetings and compliance and beating things out of like 30 different 9-5 idiots somewhere on the East Coast, which I would be ecstatic to delegate to a manager or a PM, who can run the whole project, track the timeline and answer the endless questions about when it's going to get done already. On other projects with less human dependencies you really don't need one.
I like my manager.