Jabber, I don't think writers are good at editing their own work. After all, writing coaches urge writers to stay in writing mode, and not go back and edit their work during the creative process.

The process of mentally switching to editing mode disrupts the creative process. If a writer starts editing during the writing process they're no longer CREATING.

As you say, publishing houses, even newspapers, have fact checkers and editors -- separate people from the authors -- and they wouldn't do that if there wasn't a good reason for it.

All of us, as writers, review our work periodically and make the corrections we see.

But it takes a different part of the brain to edit than it takes to write. So while a writer might see and correct a few errors in their own work, it really takes "fresh eyes" to see everything.