It just... it writes badly, because of all this biasing. I find NovelAI more useful for getting over blocks, regardless of its much lower intelligence.
Not discounting NovelAI, but you can also sign up for regular GPT3, which allows you to edit the output and generate new output based on that; as well as the option to have GPT insert text at a specified mark in the middle of a text, or have it edit text according to instructions (like "make it rhyme"). I think the regular GPT playground is a much better interface for prose than ChatGPT.
At least at NAI I can edit its output.