Generalities like those drive me slightly nuts.

"Christian bookstores sell a lot of books": Yes, it helps if you're selling the Bible, the all-time best seller.

"Millennials are the biggest buyers of books": They're the largest demographic group, so why wouldn't they be?

"Millennials like memoirs": Yes, and they also like Colleen Hoover. And I suspect that if you compare sales figures for today's best-selling memoir with any Hoover novel, she'd blow the memoir out of the water.

I hear so many generalities like those from people who "heard it from someone who heard it from someone who heard it from someone with an agent." It doesn't mean they're wrong, but they can offer false comfort to writers who, in order to succeed, need the truth above all.