What people in these comments (and really, most places on the internet) fail to grasp is the role of the publisher as a curator and editor.
Unlike your friends, the editor is not your friend. They don't have a stake in your ego, they won't sugarcoat it beyond the veneer of professionalism. You need an editor who is not your friend, too say no to you. No, you shouldn't start your book with this cliché. No, you shouldn't have your character meandering aimlessly. No, you shouldn't use whedonisms. Exceptions apply, of course, but when the editor is your publisher and not your friend, "shouldn't" becomes "can't". Usually that involves saying no to 99% of manuscripts coming through the door. And this is how an okay story becomes a great book. Your editor, having read more books than you in their segment, knows the difference... usually.
All manuscripts are at least a little bit bad, some books aren't. As you can tell, I'm no fan of self-publishing, I just don't believe anyone can be objective enough with their own baby.
Now... I've read my fair share of bad books, especially recently. The publisher/editor is to blame 95% of the time. My theory is that being rigorous takes time, which is always in short supply, and skill. I believe people tend not to stay in the same role for too long anymore, lest they lose out financially. Which is totally fair, but skill (and the chutzpah to say "no") takes a while to develop, years really. And no one has "years" for anything.
Except, of course, all the people in the industry who don't mind being poor. And people making bank, I suppose, but these are so few as to be statistically insignificant.