« And don’t use the same word repeatedly — it’s boring. »

This is dangerous advice, and not just because (as others have noted) it can add ambiguity.

Finding alternatives to the simplest word for a concept will often narrow the audience. For a simple example, if I decide I've written "Venus" too many times and substitute "the second planet", I'm unnecessarily making it more difficult for people who don't happen to know the order of the planets.