Polymath || KoG Spoilers

"Why doesn't the final character design ever look as good as the concept art?" Because the designs they come up with in concept art are iterative and are often found to not be easily readable in 3D space under different lighting conditions or with different facial expressions. They also have to be easy to animate when budgets are constrained, and have to be possible to make into a toy for merchandising. There's also just plain old marketability. A design that's too exotic risks alienating potential audiences. That means it has to follow current trends and recognizable shape language. Also, sometimes the concept art you see is from a completely different conception of the character. A character's personality and role in the story can change significantly over the course of production or development, sometimes going from a villain or side character to a protagonist or vice versa.