I am not an actor. Except for a brief stint in High School (over 20 years ago) I don't have any experience for what I am about to say. But on Free Republic everyone is entitled to post no matter how uninformed so let me say it anyway.
I suspect that film acting and stage acting are as different as swimming and SCUBA diving. On stage there is a continuity of the story that the actor can involve himself in. Even a poorer actor doesn't need to work to conjure up the sense of outrage Aldonza must have felt after being raped by the muleteers in a stage adaptation. But the screen actor may shoot the scene over one character's shoulder before lunch, stop to eat, then shoot the exact same scene after lunch over the other character's shoulder. The actor has to create that sense of outrage even if this was the first scene of the movie filmed and the actual rape scene is one of the last.
I remember when watching the "appendices" of "Fellowship of the Ring" one of the actors talking about what a pro Sean Bean was. They filmed his death from the perspective of looking at him before lunch, then filmed it from the perspective of looking at Viggo Mortensen after lunch, and he played the scene equally well both times. The very thought makes me want to laugh.
Anyway, that's just my thinking. Julie Andrews probably thought like you when they cast Audrey Hepburn as Liza Doolittle in "My Fair Lady" - until Andrews won an Oscar for her role as "Mary Poppins."
Shalom.
If you can do it before a live audience then you can do it before a camera.
Julie Andrews would have been just fine as Liza Dolittle. She was not chosen because she didn't have any box office pull while Audrey Hepburn did.
Audrey did a fantastic job. Julie Andrews would have done just as well and been able to sing Liza's songs. Something Audrey could not do. Or Natalie Woods as Maria in West Side Story.
You are correct, but competent actors do both. Most well known Hollywood actors do some stage work to sharpen their skills, and nearly all British actors perform on stage.
The problem I see in Hollywood is not in production or acting; it is in the scripts. Most are pathetic. Even blockbuster movies with expensive special effects are painful to watch a second time. Science fiction is the worst offender.
the other category of bad script is the one in which all the characters are rotten, the situation is rotten, the aftertaste is rotten. Who wants to pay money to spend an hour and a half with people you would edge away from in the subway?