Not really. Some of the best stories I have ever read was a novella told from the perspective of an autistic five year-old child. The story has limited grammar and basic vocabulary to reflect the narrator and it was fascinating to read. Sometimes the way you write is not necessarily dictated by you, the author, but rather the narrator of your story, specially if you're using first person narration or even third person limited.
If your narrator is a an uneducated thug from the underbelly of some urban city, you can't expect him to sport fancy words and flowery passages. There is a context and a color to language. If you're writing your story through the omniscient viewpoint, then you have to take into account the genre you're going to write in. Fantasy and historical fiction both take into account world-building and history so the language needs to have a serious and articulate tone. Romance prefers evocative and expressive language. Sci-fiction and action are known to have straightforward, direct and blunt language. So you should ask yourself, what genre am I writing ?
Anyhow, this is just my personal opinion but I remember reading a book by an author who wrote a lot of poetry before writing prose and her vocabulary was amazingly rich and complex but I ended up skipping half of the book due to that. It was too pretentious for my taste and of half of the novel ended up being descriptive passages and 'metaphysical' rambling which I didn't care to read. I just wanted to know what will happen to the MC after meeting the antagonist for the first time, not an academic philosophy paper. So my advice, just be balanced in the way you write, sensitive to your narrator and mindful of your target audience.
You don't need big words to write beautifully. One of my favorite quotes of all times is by Franz Kafka : "I am a cage, in search of a bird." simple, yet evocative. It creates an image for the reader and gives you a hint as to what kind of person Kafka was. Another example is the famous simile from Terry Pratchett's Guards! Guards! : "Lady Ramkin's bosom rose and fell like an empire." So, the verdict is don't write big, write smart. There you have it.