Actors deliver dialogue, not writers or directors. Lines on a page are impossible to judge.
Scripts are blueprints.
A really good actor can make the most ridiculous lines sound incredible. That fact, as much as anything else, is the very foundation of Hollywood. The ability to competently deliver utter nonsense created the star system. In Britain screenwriters are generally far too self-conscious to write nonsense and thus we end up with 'realism'. If that sounds a bit too cynical for you then try delivering a single line from a Hollywood movie in everyday life.