Think of it like a joke you've heard a thousand times. It might have been funny the first few times, but now it's just predictable and boring.
Here are some synonyms for hackneyed:
* Clichéd
* Banal
* Overworked
* Trite
* Commonplace
* Unoriginal
* Stale
* Formulaic
Examples:
* "The movie's plot was full of hackneyed tropes, like the damsel in distress and the evil villain."
* "His speech was full of hackneyed phrases that made me roll my eyes."
* "The author's writing was so hackneyed that I couldn't finish the book."
In general, it's best to avoid using hackneyed language in your writing and speaking. Try to be original and creative in your expression.