From what I've seen two things can kill a game: stagnation and changing too quick. Before I get into that I will say I'm a big fan of games where the story ends. I'd like a game where the game has a metaplot that has some sort of endgame from the beginning, whether it's "seasons" or a different phase, I'm a big fan of games like that.
Changing too fast: There was a DnD game called Treyvan. It was fairly successful, had a good number of players, active plots, etc. Then one day staff announced they were changing the theme, nobody could keep their characters. Basically, it was a different game. Treyvan died.
It changed too fast and players weren't ready for it.
Stagnation: Wanna know what will make me log out and never return? A stagnant game. If I log in, a game has a good number of players, healthy ooc chatter, but an empty grid or I find myself paging people to rp and everybody is like "nah I'm good" goes back to idling. I'm out!
Games can get stuck in a rut if they've been running for a while. The Mu I'm playing right now has been around for 20 years. I've seen people say it's dying or its stagnant. In a lot of ways it is, but they're changing it just enough where they're maintaining a playerbase. Story wise it's pretty much the same game though. The difference is there is a large number of stories you can tell in the setting.
I think someone said listening to players is useful in knowing what should be added or subtracted from a game. But I'd take it a step further and look for feedback from newer players since that's what you want, newer players coming in and adding their stories. What's keeping them? What's scaring them off? What can be done to keep that balance of keeping players and adding new ones?
