Most writers will tell you that an editor will take a great piece of work and turn it into something good. Of course, most editors will argue that it is the other way round. They can't all be right? Who wins?
Not true. The author rules. Of course, he/she may not get another contract. I never noticed any contractual provisions about obeying the editor. But there is the line about delivering an acceptable version when all is done. I suppose they could twist that into rejection. I believe at that point you lose the rest of your advance and the book doesn't get published.
My editor's quite good about giving me stylistic free reign, but at the same time gently nudging me about plot holes and loose ends, etc. Her suggestions are always commonsense and in tune with what I'm trying to do. I'm lucky--she gets it.
Personally, I've had suggestions handed to me that I knew were glaringly ridiculous. Most of the time, though, any critical suggestions I've received were right on the money. It's worth risking the former to benefit from the latter. 99% of everything I've ever been told has improved not only my WIP, but also future works.
I think it was the baseball manager Dick Williams who said that a great manager can win maybe 5 or 6 games a year by making the perfect strategic move during a game but he can lose 30 or 35 games a year by meddling too much.
Good editors are like that.
Remember, they bought the book because they like it.
I'm a short story writer, so when editors have a go at one of mine, there's not a lot of room to go crazy. Editors at Woman's World changed the title of a story of mine - to a much better one! Editor Michael Mallory turned an okay little murder story of mine into a really good yarn in the anthology "Murder on Sunset Boulevard," just by changing a couple of sentences and ditching a couple of words. I love what a good editor can do. On the other hand, I submitted a flash story a couple of years ago to a freebie start-up and the editor wanted a complete rewrite. It was a flash - less than 100 words! I declined and placed the story elsewhere.
I submitted a story to Thuglit last year, and the editors came back with a suggestion that made it a much better story, as it better conveyed my vision for the story. That's the kind of editing I can get behind. I don't want an editor to tell me what story he would have written in my place, or how he would have told it. Jsut help me get my story as good as it can be. If the story's a loser, that's on me. I'll get over it.