Obviously I can't talk for everyone, we all have brains that work differently, but I never got much help from "how to write" books. Lot of times they're wrong, and a lot of times they abstract things at a level that I can't actually absorb until I've done my own leg-work growing and learning anyway...and at that point, I'm beyond where I need any help from how-to books.
For me, the best teacher was going to novels and stories in my genre that were actually being published, reading them, and observing my own internal reactions to them. And I never saw any internal difference between how I reacted to first person or third. (As a reader.) Like, there really wasn't any greater or lesser "worth" to them. It's just a technique.
Generally, I think observing what is actually going on out there is more valid than what someone else has taken away from it and tried to codify in a how-to book. And yeah, if all YAs this year are first person POV, it perhaps suggests that there's nothing "newb" about first person at all, if you have a professional level of writing skill. Real-life data trumps what a how-to book says.