I agree. ChatGPT just cannot be succinct no matter how many times I try. But it works with GPT-3 playground, I'm able to get much better information/characters ratio there.
Don't you just give it a word length, or number of sentences, or "rewrite, but half that length"? Those sorts of things have worked well for me. "Make it sound more exciting" or "tone down the excitement level" as well.