Related to your point, George C Scott apparently didn’t want to film the opening scene of “Patton” because he thought the movie wouldn’t live up to the scene. It really gets at the heart of what the whole movie is about and I can’t imagine it without that opening. Apparently they filmed it at the end of filming.
https://en.m.wikipedia.org/wiki/Patton_(film) (The opening scene under “production” - sorry on a mobile device)