I have absolutely no idea where you've got this idea from. I've worked with dozens of directors in my 20 years as a professional, I've met and discussed film with hundreds more and I've exchanged experiences with hundreds of my professional peers. Not a single one of them would share your view on the role of the film director. Of course the Director's role is not to record the sound, edit the picture or mix the ADR, any more than it's the Director's role to act in the film. The Director's role is to direct the film, all of it, not just the actors, maybe you're getting confused with the role of Acting Coach? I've never known a director not to spend every single minute of the picture editing not sat next to the editor. A director not to direct all the ADR sessions or not to be directing the final mix is unthinkable! I've never even heard of such a thing, let alone experienced it. Producers maybe very pro-active or you may rarely see them but whatever the level of direct involvement of the producer, the director is always present, directing.
Why then is an acting coach called an acting coach and not the Actor's Director? My 'idea' of a Director comes from working on sets. Take for example a television show with a different Director for each episode - it's hardly the Director's
job to oversee the entire thing when they're only on for one episode. That's why there are other roles on board. Just as I know some Directors will sit there and dictate editing choices, others won't. Others are brought on simply to serve the purpose of directing actors. Sure, if a Director is also the writer, or has been brought on in the writing stages, perhaps they will want greater control over the picture. However, I don't know many Directors who would describe the main part of their role as 'dictating the edit' for example. Even someone like Fincher isn't there for the entirety of the edit, or the sound design and rather comes in at points and critiques what he likes and doesn't like - much the same as the DoP sits in on the colour timing with the Director. You couldn't say that the
main purpose of the DoP's job is to sit in on the colour timing, but it is an aspect. Just as possibly dictating edits, or directing actors on an ADR stage is part of a Director's job, but it isn't the reason a Director is brought on board. Also, in my experience it's people like Sound Re-Recording Mixers who, along with the Director, help decide what parts of sound should go where, not the Director's alone. Hence why experts in other fields are hired. The Director certainly has the final say, but it is not necessarily in his job description to sit in on the edit, just as it's not in the DPs job description to sit in on the colour timing. DPs do it these days to have more control over their images, just as Director's do it to have more control over their films. Does that mean the main focus of a DP has changed? No. Why then, should it mean that a Director's main focus should change?
Not only is your information incorrect but your argument makes no logical sense. First of all, contrary to your statement above, not one of the creative departments have a specialist in charge of them.
Take for example sound, the Supervising Sound Editor is, as the title suggests, a supervisor, the head of the sound department, but the supervising sound editor is not in charge of the sound, the Director is! Logically, your argument only makes sense if the director does all the acting themselves but of course they don't, they hire acting specialists (actors) to do the acting, the same as they hire a specialist editor, DOP, composer or supervising sound editor and all of them require an equal amount of focus and directing.
What purpose then does the Supervising Sound Editor serve? They may take cues from the Director, just as a DP does, but at the end of the day the Director isn't the one lighting it, operating the camera, shooting the shots... Whilst it will often be discussed with the Director, why would the DP sit down with the Production Designer to design the look for the film in Pre, if it is the Director who is in charge of it?
If the Director's role is not to focus on acting, who then dictates what the actor does? Or are they left to their own devices, forced to 'direct themselves'? I was not suggesting that other areas do not require directing, but one could also not assert that the actor's do not require directing. If a Director's main focus is not the actors, why then is a DP, Production Designer, Editor, Sound Designer etc. hired? Why not simply hire a Camera Operator, Set Dresser, Edit Assistant, etc.? If the Director must focus on all of these things at once, why does he hire seperate specialists to do them? If a Director's focus on set is not the actors, then what is his purpose other than to call 'Cut'? Micro-managing the camera? Why then hire a DP? Micro-managing the design? Why then hire a Production Designer? Running the set? Why then hire a 1st AD?
Mind you, I'm not suggesting in Pre- and Post-Production that the actors is the Director's main focus, just on set I would assert that the actor's should be the Director's main focus. Obviously he needs to have his mind across everything, and needs to ensure everything is working towards a certain vision, but the main focus of a Director on set should not be the cinematography, or the production design for example. He needs to have a handle on those things, but the main focus should be getting the performance out of the actors. To see it as merely a small aspect and not a main aspect is as I say.. somewhat odd.
Take for example a non-actor - plenty of those around, especially in children. How do you think they give such amazing performances? Just by chance? A mere fluke? Or from a Directing working hard and making sure they get a certain performance out of them?
From a technical standpoint, you could make a film without a Director. The acting would have no real direction, and may be sloppy but the film could still end up made if it was wanted to be.