I enjoyed this image but for a couple reasons I can understand the lower scores (although I do not believe it deserved and twos).
You've gotten the technical aspects nailed down well. Exposure of the subject, Sharpness, DOF, all good.
So what held the scores back?
My opinion is there is too much going on that detracts from the actual subject, the shoes. All those onions are dominating the photo to the point where the shoes seem like they were added to a photo about onions. I think if you had used only one onion the photo would have been stronger for the challenge theme. You still could have propped a shoe on it, and also maybe had a diagonal to play with in the composition. I would have gotten rid of the stem that is on camera left.
Just one persons opinions. If I voted in the challenge, I would have given this a 6 for meeting the challenge and being technically well done.