So the fancy book club people finally let someone in who hasn't read the SparkNotes version ten times. Bet they pointed out that Gatsby is just a weird neighbor who throws loud parties and stares at a green light. All that deep meaning talk probably missed that he's basically a stalker with a nice house.
A quiet comment from a new member, huh. That's how it always goes. Someone who hasn't been beaten over the head with the same old class and money talk for years can actually see the book. They probably pointed out something obvious the rest of you were too fancy to notice.
That "groupthink" thing isn't just for book clubs, it happens everywhere. Once you notice it in one place you start seeing people just nodding along to whatever the loudest person said at work and at dinner parties.