. . . Dialogue is different. People speak how they do, so you have to try to write that. You just can't go too far afield with it, or reading it becomes impossible.
Depends on the characters and their background. In Forbidden Planet
, Dr. Edward Morbius is a philologist, an expert on language and literature. He has the speech patterns of a highly literate man who chooses his words carefully before they leave his lips.
In times long past, this planet was the home of a mighty and noble race of beings which called themselves the Krell. Ethically as well as technologically, they were a million years ahead of humankind. For, in unlocking the mysteries of nature, they had conquered even their baser selves. And when, in the course of eons, they had abolished sickness and insanity and crime and all injustice, they turned, still with high benevolence, outward toward space.
Most people don't talk like that, but it's natural for the character to speak that way.