There is a rule.
“Orders are not eligible to be canceled based on the quality of service/materials delivered by the Seller if the service was rendered as described in the Gig Page. You may rate your experience with the Seller on the Order Page, including the overall level of service quality received.”
If they fail to deliver what they promised, you can cancel. If they deliver something you don’t like but it’s in accordance to what they said they would deliver, you can’t.
Example - you order a logo. Seller doesn’t deliver a logo, or completely fails to follow agreed to instructions (you ask for a blue square logo, they deliver a red round logo), you can cancel. However, if they don’t fail to meet any explicitly stated instructions (you ask for a blue square logo and they deliver a blue square logo that you think looks horrible), you can’t cancel.
Therefore, be as specific as possible in your request. If you say “Do whatever you think is best, use your creativity, etc.” instead of specific instructions, it’s your fault, not the seller’s.
This is an insane policy, and I would refuse to work under those conditions. According to that, any buyer can get any work they want, tell Fiverr “I don’t like it”, and I worked for nothing. Lots of people out there won’t be “happy” with anything, and even more would say they aren’t even if they are if that means they would get their money back and keep the product. I’m not stupid, thanks.