Agree. Fancy' words can add flavor to the writing and help avoid repetition, and also are more precise. If you are writing warning labels or instructions, then maybe simpler is better. But otherwise, I don't think it is a problem..
More precise words aren’t always better either. Having someone easily grasp what you are saying works much better for conveying information.
Complicated writing is lazy writing. “If I had more time, I would have written a shorter letter.”
If I'm reading a longer novel I want to be exposed to older, lesser used words. I think it is fun and interesting to learn new words.
You can intentionally write in a way that's different from your natural voice if your goal is, say, information density, or expressiveness that conveys personality or that makes the experience of reading more enjoyable, or to allow writing to shimmer with all of its contextual entanglements.
Of course people can attempt to do this and make a reading experience worse, and I think writing how you talk can be a helpful rule of thumb for certain use cases.