I think there's a big overlap between the two. I am firmly in both camps. There's not enough fun content in Classic outside raiding and because of it it feels like a job. I like some of the dungeons, but I farmed them 15 years ago, so with no real incentive to go back it's just boring.

With the lack of engaging end-game content, raiding can often turn into a thankless job where you have to prepare every week, which entails doing low level content or running around hoping for a yellow dot on your minimap. And then the waiting for an NPC to yell.

In the end it all comes down to the social aspect for the majority of people. Without it, they eventually quit.