That's a fair criticism and results from the fact that we used an asset pack for the background during prototyping just to quickly churn something out. The line and trail renderers took me a couple days slaving away over a hot Editor, but I'm chuffed to bits with the result; whereas the characters themselves were just placeholder box and circle until more than halfway through the jam. Reason being, we wanted to focus more on solid gameplay, with the art being polish on top.
For a more-expansive build, we'd definitely remake everything from scratch to unify the style, as you point out.