They would need a story and setting that pulls me back in again. While there have been some side stories I've enjoyed, like Velen/Draenei stuff in Legion, the internal Kul'Tiras arc in BFA, most of the main ongoing storyline stuff I haven't really enjoyed much in a long, long time.
RP is what keeps me around and invested in an MMO. And being invested in RPing in a MMO means being invested in its lore, story and world. Having lost that investment in WoW and its world, I don't have much urge to play. I only played WoD and Legion on and off. BFA I barely touched after launch. Shadowlands I just have zero desires to touch at all.