The fallacy there is that I am not merely "building a team," I am managing. Managing is a live, interactive skill that involves certain services. A perfect team still needs management to help create the environment in which that team can effectively operate.

I saw a wonderful interview with a former commander of an aircraft carrier. (https://www.youtube.com/watch?v=b9rGATwZRr0) Rear Admiral Mike "Nasty" Manazir speaks of his main job as being clearing away obstacles that no one underneath him could clear. That's a service that no "self-managing team" can do for itself. A good manager also serves as a focus for the strategy, and deals with conflicts that would otherwise become impasses.