Really, I would have thought there would be lots of English majors available for remote work? I know nothing of publishing, what distinguishes a good editor?
It's far more than the mechanics of the writing.
Many editors aren't great at the mechanics, either. Axiomatically, proofers aren't editors, and editors aren't proofers; neither are layout techs and layout techs often aren't editors. Note that I have done some editorial work, and am too dyslexic to proofread.
While the average 4th year English major can proof for mechanics, they're going to need to know the subject matter, and play devil's advocate for what needs cut, what needs expanded, and what is right decisions.
A good editor is the author's partner in design - things like "That's the wrong term" and "This is clear," "This is a duplication of...," and "This is unclear." And sometimes, "WT_ ARE YOU SMOKING???" whilst indicating a paragraph.
They also are the layout guy's collaborator in what, where, how.
And the person on the lookout for consistent Tone and Voice.
In traditional publishing, the editor is also often the author's supervisor... in the games industry, sometimes so, other times, other way 'round, and sometimes, both are employees of a third.. Which creates an interesting dynamic - the editor isn't the talent, but is reliant upon the talent to produce so they both get paid.
That's a bit meandery; I'm not quite sharp enough tonight to clarify it.