Trade publishing can put its books in every bookstore, and get its friends in the media to push them constantly. But that becomes less useful every year.
I doubt we’re ever going to see another Harry Potter, because the mechanisms that made it so popular no longer really exist. While the publishers have every TV talk show talking about the book, we’re watching Netflix and Youtube.
That doesn’t mean Stephen King has anything to worry about, because he has a popular backlist and and established fanbase who’ll buy most or all of his books. But creating another King will be much harder. Another Rowling, probably impossible.
Trade publishing isn’t going away any time soon, but more and more new writers start out in indie publishing and need a very good reason to consider a trade publishing deal.