I think the first duty of all art, including fiction of any kind, is to entertain. That is to say, to hold interest. No matter how worthy the message of something, if it's dull, you're just not communicating.
I think as novelists, we consider ourselves artists and many claim to be literary writers. Many write poetic lines or use big words in the hopes of sounding brilliant, winning a prize or acclaim. However, if the reader spends more time with their dictionary or on Google or if the reader needs to re-read passages over and over, they aren't really developing attachments to character or plot. Will your story have the same affect if the reader believes you're trying to sound smarter than they are?