Yes people are buying John Grisham and JK Rowling and the latest celebrity memoir, but eventually (1) interest will run out and people will want the next new thing and (2) these big brands will realize that they don't need the publishers to market for them (and this is already happening, as the article says). What then?
It's often the same publishers publishing the e-books. They did successfully make that transition.
> Instead they went all in on pulp bestsellers and celebrity memoirs at the expense of actual good authors
If they're best sellers, as you note, that was clearly a good choice. They were selling what people actually wanted.