"If you care about being thought credible and intelligent, do not use complex language where simpler language will do."

This is a quote from a Nobel-prize winning psychologist in an article that didn't actually have to do with writing, but this definitely applies.

I see it most in new writers who are trying to write anything business or academic related, but it happens a lot of any new writers, even in stories. People want their books to be super sophisticated and amazing, so they try to do that through complex prose that just makes everything worse.

Just don't. Please. Just don't.

Write like a human being and you will draw people in. I have a degree in English and have worked for magazines and book publishers as a professional writer and editor, and my biggest rule I've learned over the years is that you should sound like as much of a human being and write as close to the way you talk as possible. You need to know grammar so things can make sense, but you should break it as much as you need to to sound like a normal person that people can relate to and connect with. You'll see me writing plenty of stuff that isn't as technically perfect, and it's not because I don't know better; it's because I'm making a conscious decision to write in a more casual way.