A book won’t sell itself.
Which addresses your second point: machines can produce an endless stream of human-like text, but they have exactly the same problem as human generated text: finding an audience.
How are these endless streams of human-like text finding an audience? Most of the time they are not.
And as soon as you scratch beneath the surface there is no one to interview. No one to turn up at literary festivals. No one to write opinion pieces or blog pieces for book-interested audiences. As I said: writing isn’t the problem. Finding the audience is the problem.
What distinguishes a book that is read by no one from a book that is read by a bunch of people? It’s definitely not the writing. There are great books out there that never find an audience because no one ever went out there to find an audience for those books.