Having said that, yes, I do understand that small scenes in a movie contribute to a bigger picture; a story with themes, etc. So it is important for a director to be there and help the actors understand how their dialogue is part of that. But the quality of a separate performance by an actor in its own right should be completely independent of the ability of the director to communicate the bigger picture. An actor should at least be able to understand or perceive *something* about their character, their dialogue, and their plotlines, and act accordingly. I mean, if a director doesn't give an actor adequate direction (or any at all), the actor should be able to at the very least draw upon his/her own ideas to achieve his/her performance.
Bottom line: an actor shouldn't be an empty vessel, waiting to be ordered around. An actor should bring his/her own life to the performance.