It seems like people only play now during events. But we can't have a full-scale event (like Legacy of Bretons or Witches Festival) every week. What if we had a smaller scale mini event that was based in DLC zones? Just double drops from bosses, trials, and dailies. No new style pages, farming yield increase or visit from the Impresario.
This would provide two benefits that are desperately needed now:
First, it would make it significantly easier for new players to complete content in old DLC zones. I know people are going to say "New players can just join a guild/ask in zone chat/git gud/use activity finder/etc." Is that happening though? Like is everyone else seeing a massive influx of new players that I'm somehow missing?
Second, it would be something for old players to do. I know most of us are complete on motifs and plans from old zones, but they are something we could sell. Plus we'd get valuable style mats for use/sale.
I'm not saying this will completely solve the low population issues ESO is facing at the moment, but it's better than nothing. If we wait too long to try new things to bring new players to the game and old players back, it will be too late.