Do you find opinionated essays by persuasive writers to be "manipulative"? I view Adam Curtis documentaries as "intellectual essays in film/narrative form".

There is another kind of documentary, e.g. the Ken Burns style, that seems to take no position, similar to a piece of journalism. This is simply a different style of documentary.

You should check out Werner Herzog's "Lo and Behold", which may be at the center point of these two styles. In that film, Herzog is clearly stating a point of view, but the visual structure -- its scenes, setup, cinematography, and structure -- borrows from the journalistic style. If you put these three styles on a spectrum, perhaps then you will find the style itself isn't worth debating, just as George Orwell vs Jorge Luis Borges may have been writers of very different styles, but very (nonetheless) interesting content.