Who is actually in control of a film, is it necessarily the director and if so how much control can they exert on a production, and who can ultimately override any decisions made by a director?
On studio films the answer is; it depends on the contract. In some
cases the studio head has final say and the producer and director are
contracted to follow their directives. Sometimes the producer has the
control. And in a few cases the director has the final say – we have
all heard stories of directors with final cut losing control and then suing.
Some producers are very creative and will sit in the editing room and
make excellent suggestions. Not all producers are fools with a checkbook.
Some actually love movies and actors and the creative process. And some
are even good at their job.
So you are right; there is a misconception by some people that directors
are the ones who are always solely to blame for a film's lack of success.
The thing is though in regards to acting, when it comes to editing and choosing the best take of an actor's performance if the producer says they prefer the take where an actor was doing or saying something one way but the director doesn't like that take, and the producer overrides the director then can the director still be blamed for not directing the actors in a better way?
But you're asking about assigning blame. I don't believe it's that simple.
If there is a dispute in the editing room over a specific take of an actors
performance all three people involved are to blame (or praise). But that
doesn't stop some people from thinking that directors are the ones who
are always solely to blame for a film's lack of success. It's more complicated
than that.
When it comes to the success of a film even marketing can take some
of the blame for success or lack thereof. In almost no movie is there one
person who should take the blame (or praise) for a films success.