In a perfect world, publishers would do what they did in the past, i.e. contribute to giving feedback on the contents and the title, proof-reading and copy-editing, making the cover, taking some financial risk by printing the book, distributing it to a pre-existing network of bookstores, sending it to book reviewers prior to releasing it, and promoting it.
In today's world, they kind of still do that, but spend so little time, energy and money on it that it's impossible for them to even remotely justify the huge cut they take with a straight face. Innate talent left aside, whether an author wannabe's book sells well or not entirely depends on his willingness to promote it by showing up at events and bookstores.
As such, you're just as well off -- and more often than not, better off -- relying on friends for feedback and copy-editing, self-publishing an ebook, and reaching out to your audience directly through mostly online channels.
(I worked in a brick and mortar bookstore, and have been watching the situation degrade over the years ever since. Methinks that, much like the press at large, publishers only have themselves to blame.)
