Editors does a lot less for quality of the writing than people tend to think.

Also, there’s nothing stopping someone self publishing from getting an editor to polish their manuscript before publication.

The truth is that most authors who self publish are simply not good at writing.

I am generally a fan of self publishing, it’s great for good writers as they get to keep more of the money and for the ones on the border it allows them to get something out there that might be good enough for a small audience.