It seems at the beginning of the season they drop exotic emotes/ornaments much easier, so it might just be the case that you already have most (if not all) of the items they added to the pool for that season and the chance for the rest to drop is lower. Not all Eververse items are in the Bright Engram pool, though they do have a preview for what they added if you select it. It would be nice if it was able to drop only items you don't have or Bright Dust though.