Do changes in the publishing industry impact how an author should promote their book?

It is not so much that the publishing industry is changing, it is mostly in the way that people are consuming media and the explosion of competing noise signalling attention. The publishing industry has struggled to adjust to this new reality but what has emerged provides new opportunities for authors and publishing companies.  The larger companies will continue to fight for surviving of their revenue streams.  Indie publishing is easier now but much harder to making enough money for it to be sustainable.

It has always been a challenge for authors to find an audience willing to pay for the work.  It is not any easier now.

Online and offline, it is all about marketing, and that requires funding, something that the publishing companies do not do now without some proof that an author has an audience of buyers.  Celebrity wins in this game unfortunately and while a few authors are able to bust through, they are not necessarily the best writers or the best books.  Nothing new here, great literature has always had a limited audience.  Fun novels, like tabloid newspapers, will find a ready audience.

I have found that similar to the music business that to sell a book or recorded music one has to promote in person.  Online marketing through the many pay to play advertising schemes is also necessary but it is not as effective as doing a talk or performing the music.   This reduces the book and music to a complement for the creator and with the exception of creative writing the books are reduced to a commodity.