A very depressing question for me. And a hard one to answer
As someone who hasn't played WoW for just over a year now and has been unsubbed for that long also, Its a very hard question, one you cannot fix with 'just make a good game'. There are so many intricacies and layers. Blizzard could release the best expansion after Shadowlands and I dont think thats going to bring me back. I think its just time.
I feel its something that's just not going to happen. I just don't have FUN in WoW anymore. I find everything in the game work, a chore. since I quit WoW I been playing games and having fun, something blizzard haven't provided for along time. The only things I get from WoW is anxiety, frustration, stress and obligation. I feel like I was playing because I been leeched onto the company since 1993 I felt I had to.
Sad times seeing as someone who used to play every blizzard game (except HotS, I suck at MOBAS), now doesn't play a single one. And thats not me boycotting the compony for whatever reason, oh no. Over time I slowly just stopped enjoying Blizzard games... It wasnt even intended or anything, it just happened. And I haven't went back to a single one, I just moved on. Very sad actually
I'll always have the memories though. what a ride.