> A single person taking the role of director/editor/screenwriter is pretty much unheard of in the industry.
Wrong.
Let's take a very recent example (and note well, this is not at all uncommon outside of Hollywood, for instance Teshigahara's famous collaborations with author Kobo Abe) Paul Thomas Anderson, directed, wrote, and produced/edited (both the 65mm and digital transfer, in tandem) The Master. It is not at all uncommon for a director to at least collaborate with a screenwriter if not write the screenplay themselves. And most directors would like (although this is sometimes prohibited by the studios, e.g. in the case of Orson Welles) to have creative power if not direct control over the production and editing process.
However, even at this level of involvement we are a far cry from the claim that a single person is responsible for the film as a creative work.
For instance, you're missing a critical piece of the equation: acting. You could easily make the argument the job of an actor is as important as any role a director might have and ultimately it is the centerpiece of so much film as well as the final artist presentation. Even the most controlling directors have limited ability to hold de facto control over this aspect of the film.
Considering all the multitude of complexities of the process, the myth of this superhuman director here is a lot less interesting than the actual process of filmmaking, if you ask me.