I agree with the other commenters. "Too much white" was not the problem / critique. The issue they were pointing out is that the whole image has the same value /weight to it.
By "values", they mean shades of gray (which can also be accomplished visually with cross hatching), or if it's a color piece, the equivalent of different shades of gray in the colors (red is a "dark" color, while yellow is a "light" color, etc.). I don't know much about color theory, though!
If you study design principles, one of the things you learn about is "hierarchy" -- meaning, "What is the focus of the image?", or "Where am I supposed to look first?" You can recognize this easily in text. If you see a sign that has some words in big, bold letters and other text in smaller letters, you will probably read the big bold words first--even if the bold words aren't at the top of the sign. Bigger, smaller, brighter, darker -- whatever is significantly "more" catches your attention.
Hierarchy can be achieved through different techniques. Basically, you want something to be different -- and often you'll have more than one aspect or quality that's different than the things around it. Big/Small, Light/Dark, Warm/Cool (colors), Detailed/Vague, etc.
Your eye should be immediately drawn to the main part of your drawing. I've often heard our SVS teachers talk about 1st read, 2nd read, & 3rd read. What is the first thing you see when you look at the picture? What is the second thing you notice? It should only take a split second to notice the 1st thing. You should see it immediately -- without thinking or effort. By the time you get to the 3rd thing, it's ok if it takes some time & paying attention to see it.
It looks like you may have considered having different sizes -- the fairy is bigger than the turtles. Although, the turtle on the rock does make a shape similar in size, so you want to be aware of things like that. Maybe you can practice by circling the general shapes in other people's work, and your own, to help notice the size differences of different shapes.
Another design principle you can use is "Contrast". High contrast is when you have something white next to something black. Low contrast is when you have colors of similar value. For example, a black horse on a white background is a high contrast image. Line work is usually not thick enough to count as "black" or "white". You need to consider how dark or light the character or item is overall -- compared to the background, or whatever is adjacent to that object. You want to be able to zoom out & squint your eyes, and still be able to see a distinct silhouette. Your original image is low contrast, because all the objects in the image have about the same amount of shading, and all of the marks on the page are pretty evenly dispersed.
When they post the critique arena video (https://courses.svslearn.com/courses/take/critique-arena), go back to the part where they compare the group that made it into the top 16 -- next to the group that didn't. All of the ones that didn't make the cut had very little contrast. It's ok to have a low contrast image, but it will have a hard time standing out next to an image with higher contrast, and it will need to use other techniques or "design principles" to make the image "readable" and interesting.
I hope that helps explain it!
It's great that you're putting in the effort to learn & use the advice / critique of others to improve your skills. You have a great attitude!
