There are many horrible self-published books in need of a proper editor, this is one thing publishers facilitated at least.
This is true, however many of the authors self publishing on Amazon are very good about getting out updated, properly edited versions. I get email notifications all the time about e-book updates from Amazon, and many have huge improvements. As they make money new authors are better able to afford editors down the road.
“The greatness of a nation and its moral progress can be judged by the way its animals are treated.” - Mahatma Gandhi