Hello Max! I think that this drawing is lacking a variety of edges, I'm mostly seeing hard and firm edges, you need to get better at making and identifying where to make soft edges, remember that learning art is more learning to see than learning to paint/draw. That skill of observation will develop by observing instructors interpret references, watching them draw and you being aware of those decisions, or at least I think I improved the most that way. As for the technique, you also need to practice making soft gradations so you can make a form turn beautifully, keep practicing the simple forms, balls, cones and you'll get better