Plastic wheel well trim looks horrible

Use the spray on tire cleaner or what manufacturers call tire shine. Various manufacturers make their own stuff. Can get it at Walmart or any such store. The kind you spray on a tire and let it set. Some are no wipe, others recommend wiping it on. Extremely easy to use. Spray on and forget it. Doesn't hurt paint or chrome. Brings rubber and plastic back to shiny black finish again. I've used it for years on the RV trim and tires, car and truck tires, black plastic trim on vehicles like around the bumpers, truck beds. Also use it on the inside like dash, door panels, instrument panel, etc. Anything with black plastic pops out bright shiny black. It's what used car dealers use it on their cars before putting them on the lot.
Don't paint. Paint will chip and peal then look worse than what you have now and you'll have a mess trying to get it to look better after that.