Some of my submitted assets (pictures) have not been moderated and released for several months.

Adobe no longer reliably adheres to the "first-in/first-out" process, and review times can be widely variable and unpredictable. If assets haven't been reviewed after several months, they may get stuck and ignored for a very long time. I have some that waited for ~11 months. I have tried deleting and resubmitting with minimal success.