Maybe, but I think it’s just the idea that it doesn’t need to be mutually exclusive.
If you play an MMO, you are probably there primarily for the community/group/social content, the character builds, the economy, the frequent updates, etc. But nothing says it can’t also have a good story.
To use FF14 as an example, as the only one I’ve played, the story could probably be told just as well in the form of a single-player game (or, being more realistic given its size, a series of single-player games). But it exists in the first place because there is a market for people who like both MMOs and the kinds of stories told in Final Fantasy games. For people who aren’t into the online elements, there are still plenty of good single-player experiences out there, like maybe the 14 other Final Fantasy titles that aren’t MMOs.