As Creatives, we provide content, not books. Books are packaging, just like CD’s used to be. And now, new cars don't even come with CD players. The world has moved on from the old ways of publishing too, including all of the self-publishing platforms we've come to know. Creatives are becoming pseudo-celebrities (medium fish in small ponds), a status they're leveraging in what has become a gig economy - many baskets of visibility - many baskets of revenue.
Sure, the top percentile of any group is doing fine, but they're not the ones driving the boat anymore, it's the next generation that's reinventing entertainment and how we access it. As I've said before, get all you can out of the current system, for as long as you can, but it's way past time to rethink our content (product) and how our fans want to enjoy it. New tech is coming. For productivity, tablets are merging into laptops, but for entertainment, they're being replaced by folding phone displays.
This report is documenting the last days of the old publishing world, and doesn't really affect where things are going to go from here, just like similar reports a few years back didn't mention how streaming would change the music business.
While I agree with your distinction between content and packaging, I don't see the folding phone as the future of content.
Phones are great for convenience, like for checking email on the go, but I know literally zero people whose phone is their preferred method of watching movies. Maybe if someone is trapped in a boring situation with nothing on their phone except a movie--but how often is that going to happen? (And who's buying all those big-screen TVs that take up a huge chunk of the local Best Buy? And how well is a phone going to do with 4K video? You see where I'm going.)
Music is maybe a better fit for digital devices, but even there, vinyl records are still being manufacturing, and sales are actually increasing.
Vinyl! Its death was predicted long ago, yet now it's slowly resurrecting.
Of course, books are the most relevant to us, but as Shoe points out, many people still prefer paper books. The more my friends love reading, in fact, the more likely they are to prefer paper. I prefer ebooks now only because I'm running out of space, so I only go with paper if that's the only format available.
I'm not saying these patterns will never change, but I'm not sure when or to what. Some tech prophecies have come true, but others have fallen flat. And there is value in owning a copy rather than having it somewhere in the cloud. My heirs, some of whom are readers, can inherit my paper books. But they can't inherit my Amazon account, which means unless they keep my Kindle offline forever, they lose access to all the ebooks I own. There have all been cases of people losing access to digital content when companies went out of business. If you buy a paper book, that purchase is unaffected by the book store going out of business. (A good thing, given how many I bought from Borders!) The same isn't always true for digital content. Downloaded is safer than streaming in that regard, but not completely safe.
