Well its because the foundations are off. The drawing, perspective, values and color are off. DOnt worry too much about getting them right because you do not have much time. Focus on composition and drawing.
1-Your image has color saturation and hue and value contrast all over the place. So its difficult to read.
2-Edges: edges are incredibly important in an image. Again a part of painting that is learned in foundation training. The edges are all sharp in your image here. So there is shape and edge contrast everywhere. Again eyes are attracted and its tough to read.
3-Drawing, the girl's scale is off. She should be scaled down. The drawing of her body is full front and the vehicle is in perspective. Also the BG is not understandable. Which doesnt help.
4-COmpo: AVoid the tension near the girls head with the BG. There is too much going on in there with the pole and sort of beam intersecting behind her head.
I think you did not trace your perspective lines, am i right ?
Check this rough paintover:
I had to revert to black and white. Kill all the BG. Trace all perspective lines, and start drawing the buildings and the base where the mecha is standing on. Then redraw a bit of the mecha because you cannot draw the mecha if you have no drawing of the floor where it is standing. Also whithout perspective lines how can you draw ?
Focus on working step by step:
1-First you composition
2-then perspective and drawing
3-then add on some design and detail on the drawing.
4-Then the values
When that works....go for the painting, colors and clean render. Dont jump the steps because of time. Better to have a good black and white sketch than a bad final color image.
