Hmm... I'd say that depends on what you want for your art to look like. A friend of mine makes great artworks without any shading because they simply have no fun in doing it. I prefer most artworks with at least minor shading, but when I'm lazy I just put some lighting on it and call it a day. Overlay layers in a certain colour or gradient can already change a lot and tie it together nicely.
Well, most of my pieces are more on the side of realism, but I liked the more comic style for this one. I think what is making me unsure is the lack of definition on her coat, mostly