A writing teacher in Fresno told me to throw out my character sheets and just write what they keep hidden
I argued with her for 20 minutes, but then I rewrote one scene with a secret instead of a backstory and it did more in 200 words than 3 pages of history ever did. What is the one thing your character would lie about, and how does that change the prompt you give them?
Disagree with the whole premise here. Throwing out character sheets is how you end up with people who do things because the plot needs them to, not because they're real. The secret only works because the backstory is already in your head, even if it never hits the page. Take away the history and the lie has nothing to push against, so the reader just gets a vague mood instead of a person. That teacher got a better scene out of you because you already knew the history and finally stopped dumping it on the page, not because the history didn't matter. Keep the sheets. Just stop handing them to the reader.