I think it's more than this.Symbolism is the best way to show emotions and feelings in a movie.
Symbolism is the ONLY way to convey emotion. That's why art exists.
Why?What about dialogue,for example?It's still a way to express feelings,isn't it?
Marco, if I tell you I am angry, do you feel it? Have I really conveyed the emotion or have I just told you about it? What if I don't know what the word "angry" means? Also, dialogue can be art if it really gets you to feel what the author intended.
Wow, it's been a while, isn't it?

However, I get your point and I totally agree with you, especially the last thing you said, that is almost what I said some time ago in a previous post: the author can express feelings and convey them to the reader/watcher through the right use of figures of speech. Of course, he has to be a talented one, because that is not an easy job, but it is possible for a good writer/storyteller. Otherwise, why we're supposed to read a book?