In my opinion, Dunkirk was one of the best movies of the last decade. With that being said, Inception, Dark Knight, and most of Nolan's movies are fantastic, so I'm sure this will be great.
Ken Burns is exactly right. If the subject is involved in or influences the creation of a film about them, it is no longer a documentary. The Taylor Swift film is not a documentary. The Michelle Obama film is not a documentary. Some may be harmless and/or enjoyable to watch, but they are no longer documentaries.
Just think if the (excellent) film about Steve Bannon, "The Brink," was produced by him and only things he approved went into the film. It definitely would not have premiered at Sundance and it would not be a piece of documentary journalism.
We need another category. While "The Last Dance" and "Becoming" may be enjoyable or entertaining, they are an extended PR campaign, not documentaries. And to keep pushing them as such is dangerous and erodes the credibility of true documentary journalism.