Poly (many) syllabic (syllables) words have their place in literature, but as a writer it's best if you don't create stories that are difficult for a reader to figure out what you are trying to say. Words don't have to be made up of a bunch of syllables in order to put a point across. For the most part, we have a tendency to speak in mono (single) syllabic words because they're easier to understand and, for those of us who are a bit lazy in the way we offer explanations, they are also easier to speak and write. After all, why do you suppose we invented and continuously use contractions?
Granted, you may have a character in your story whose personality is befitting of polysyllabic words, and that's perfectly fine. When writing nonfiction, there are often descriptions that require polysyllabic words. So we can, without a doubt, say they are more than acceptable in certain scenarios. But if you want to sell lots of books, you need to make them enjoyable for as many readers as possible, not just for the top 2% of an extremely educated group of scholars who, more than likely, share specific interests. I sincerely doubt that most of us would snuggle up in a soft, warm blanket next to the fire with a cup of mocha latte and earnestly get our heads wrapped around a book called "An Overview of the Formula Used to Explain Boeing's Configurations of Left Wing Flap Movement in the Landing Procedure of a 727 Passenger Plane." And you can bet that book would contain a plethora of polysyllabic words.
But for the most part, polysyllabic words can be detrimental to your story by making the reader work extra hard at understanding what a character is talking about. Big, long words tend to muddy-up dialogue. Readers expect some characters to use big words, but only if the character would actually talk that way (Sherlock Holmes, for example). The KIS (Keep It Simple) method should take precedence in most cases. Here is one of my favorite--and anonymous--polysyllabic takes on an otherwise simple, familiar rhyme:
Scintillate, scintillate, globule vivific,Fain would I fathom thy nature specific.
Loftily poised in the ether capacious,
Strongly resembling a gem carbonaceous.
-TRANSLATED-
Twinkle, twinkle, little star,
How I wonder what you are,
Up above the world so high,
Like a diamond in the sky.
How I wonder what you are,
Up above the world so high,
Like a diamond in the sky.
