An editor can do more than just catch if there's a comma needed after an introductory adverbial clause, if 2 independent clauses are properly joined, if a word should be "saw" vs. "was", if words like "I" are omitted entirely from a sentence, if a verb performed by boats/ships is used to describe an action of an automobile, if a character started a scene out in a dress but takes pants off later on, and if all clothing items are removed except for a pair of pants before the hero plunges into the heroine. All of these things are things I'm generally pretty good @ ignoring, even though I've "paid" for a less than perfect product.
Editors can also "clean up" & "fine tune" a story so it flows more consistently. They are not personally involved w/the story as the author, so they can objectively cut out info that isn't really needed. They can also determined if all characters are essential to the story or if certain characters & scenes are best omitted. Editors objectively assess if characters have the best identifiable names so one won't get them confused with other characters. Just like when one goes to a restaurant & views a menu to consider his/her meal options, it's recommended that menus only be one page of the establishment's best properly described items & meals rather than many pages of a variety of of choices. This is suppose to ease the selection process for the customer & rely quality confidence of the restaurant. See what I'm getting at?
I like this author! I think she has a looootttt of potential! She develops strong, unique characters that can stand out amongst other characters in the sea of contemporary reads that are currently out there. I think BA has accomplished a great deal in "FZ". She is just in need of a good editor next time. I can see BA doing well & having a successful career as an author. I wish her good luck in her endeavors - with a good editor!