You're more or less right, but I don't think this is exactly the case. A good manager shouldn't need to be an expert in what their staff is doing. The manager should be there to help them let them do their jobs and stay out of the way. I always say the same thing around this, "If you have to constantly watch your employees either, why do they still work for you, or why are you the manager?"
It's not an either/or, it should be both. A good manager must be at least good at anything their staff is doing and a good manager should be there to help them, let staff do their jobs, and stay out of the way.
If the manager isn't really good at (or an expert in) the role under them, then by definition they can't be a good manager, because they couldn't actually help their staff. But a manager shouldn't be doing their staff's job (they shouldn't be micromanaging), they should have trust in their staff to do good work, and only get involved when explicitly asked, or when something has gone too far off the rails.
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It should be a "trust but verify" situation. You should trust your team to do work, and stay out of their way to let them do it, but also know enough of the specifics to be able to verify any of it and correct when necessary.
Completely disagree. I've never had a manager who was as good as me at doing my particular job, even when I was the most junior of developers and that has not once been a problem. Even the bad managers I've had weren't bad because they could help me with my day to day job. If I needed help with those aspects of my job I spoke to the project lead or one of the senior developer.
Ok sure, but a "Project Lead" is just another title for a manager. Calling your managers something else, doesn't make them not-a-manager.
You can delegate the task, but if you do it, the responsibility is now shared. It never leaves you.