Editing can add a lot to a story, but a story has to have a lot going for it before editing if it is to be successful. The author has the primary responsibility. His imagination and creativity are the first and most important factors in producing a good story. If his is a good story, good editing can enhance it to some extent.
Some authors don't really appreciate what an editor can do for the story. I've known some to respond negatively to suggested changes in wording...even to spelling corrections...as if they felt the editor was trying to take over the story. Some authors don't seem to care much for the language. English has a lot of rules and rules are there to be broken seems to be the attitude of some. It's been a lot of fun helping several authors with their work, but everyone involved has to understand that producing a story is a team effort and the author is the team leader.
Before I agree to edit or proofread for an author, I read a sample of his work. If it's very poorly written, I will decline the opportunity every time. Some authors have great imaginations and are highly creative, but are seriously lacking in language skills.
Are editors hard to come by? I think they are for some, but a good author, who takes pride in his work and wants to make a contribution to the GA community and to the language, will never have to go begging.