Quitting a movie mid-shoot, or attempting to do so, just because he personally thinks it will be bad, will do far more harm to an actor’s career than going the distance and finishing the film, even if it is bad.
For one thing, once you’ve signed up to the movie, you’re under contract. You can’t just walk away because Sorry guys, I just don’t think the movie’s going to be good for me. Something doesn’t feel right.
Secondly, plenty of actors have been in great films which they wished they hadn’t made, but which contain some of that actor’s best work, e.g. Burt Reynolds in Boogie Nights. Actors can’t always tell how good the film is that they happen to be making.
Finally, when the movie comes out, and it’s bad, professionals will be able to tell why it was bad. They won’t necessarily blame the actor for a bad script or shitty direction, and may well admire an actor for throwing themself wholeheartedly into a crappy project.
Case in point: Barry Pepper played the heroic human Jonny in the epically crappy Battlefield Earth, but nobody blames him for that horrific vanity project.
He went on to win a Primetime Emmy for The Kennedys.