This group is heavily curated, and one of the criterion is subjective preference.
You may have some work accepted then many others rejected. The curators apply this method to all submissions including their own work.
If you have work that is not accepted, do not see this as a negative criticism of your work, or that your work is inferior. This means that the work is not the best fit for the particular collection at the time. If you have work that is accepted, you can feel good knowing that your work has made it past a rigid curatorial process.
Keep making the work!