In MMOs there's not much immersion or character(s) development going on, besides from the fact that you're progression your character through artificial levels. But the story immersion is MMOs tend to be lackluster and not all that interesting. Some parts of the story is restricted in ways where you need a group of 10 or 25 players to experience, causing some players to be locked out of the story element altogether.
Now I know, some of you are thinking well what about MOBAs? They don't have any story or character immersion behind them so why all the interest? True, MOBAs do not have an inch of story development but I play MOBAs for its competitive nature. Yes, MMOs have player competition as well, but unlike MOBAs, MMOs too have restricted competition.
It's not fun joining a battleground as a fresh newly character because most likely you're be competing against other players who are much better geared than you. I don't know about you, but I never found it fun to be in a situation where you have to grind for gear just to be competitive. At least in a MOBA your character(s) are already established and ready to play on equal footing, and its up to you as a player improve your skill.
So, those are my thoughts in regards to singe/multiplayer player games compared to MMOs. Though, I believe Albion Online is an MMO that could get me back into the genre again and I know it's not going to be an MMO that's immersive in story development, but it seems like it will be an MMO that's immersed with player choices and freedom. And that's something I can see myself getting into.