When you are learning a language for the first time, it's natural to want to impress others with your newly-acquired 'mastery'. Reminds me of this little kid who came home from school saying, 'Mom, I learnt a new word today'. Mom says, 'What's that?' Kid says, 'I'll give you three surmises'. It's ok. For a kid. Not for people who get paid to write professionally.
Because communication is about clarity. It's more about how much the other person you are talking to doesn't know or care about than about your own cleverness. That doesn't mean you have to dumb it down, far from it. You just have to keep it simple and effective.
Consider this powerful sentence from Hemingway. In The Sun Also Rises, there's a passage where a few people are talking. One of them says, "And I went bankrupt". Another guy asks, "How did you go bankrupt?" to which the first person says, "Well, gradually, then suddenly." Brilliant, don't you think? And it applies to most situations in life. How did your marriage end? How did you lose your job? How did you become an expert? (Like that saying about overnight success taking at least ten years).
The power of that reply is in its simplicity. It comes from experience and resonates with the reader at a different level. There's a reason proverbs, which are distilled wisdom passed down through generations, are expressed in simple language. Truth or what passes for it, expressed in simple yet powerful words, tends to last longer and have more impact.
Floccinaucinihilipilification, by the way, means 'to regard something as worthless'. As in floccinaucinihilipilification of unnecessarily big words.