Every single solitary MMO, I was dragged there kicking and screaming by IRL friends. I never M... MO... but played where they played.
If it was group, it was group. If it was raid, it was raid.
EXCEPT
City of Heroes. They left because it was EZMode and that's the only one that I could solo the "solo" missions... which is also why it failed. "Why solo in an MMO?" type of thing.
"I dunno. My friends dragged me. Ask them." But City was just at "my" level to keep playing. Loved the Character generation (for 2004, it was great). It was cancelled, though.
And to this day, I play a mission or 3 a day on an actual licensed pirate server (!). Yeah, NCSoft said: As long as you don't make actual profits, here's a license.
But if you like challenges and HAVING to group/raid, barring about 5-10% of City of Heroes content: it's a solo / play with friends game. Avoid if you're hardcore.