It's probably due to Scott Snyder fumbling as a writer (dropping a plot thread and/or taking way too long to actually conclude it or build upon it, while ignoring a character in his roster). As I've said before, he probably does not have much interest in Green Lantern compared to the other toys he has available to him. I'm guessing John is only there as a nod to the Justice League cartoon, not because Snyder has anything particularly compelling for the character.
I don't think editorial had much to do with this, partially because it seems like such little editing goes on these days. If I was editor, I would
at least inform Snyder of my concerns and criticisms of his work, especially since the sales on the book are relatively tepid. However, that would be a risky political maneuver, because Scott Snyder is a much bigger name in the industry than whoever is editing Justice League.
Some creators having too much power and being able to do things willy-nilly is one of the problems with the industry these days. Meanwhile, the editors don't often seem to have much of a cohesive plan or vision for their characters, or much coordination between themselves. Some people jump on Jim Shooter for being a tyrant, but all I really know is he was never afraid to veto creators who were doing or wanted to do stupid crap, that he took Marvel out of the gutter, the comics sold a lot better in his day, he introduced a lucrative and innovative market for the time, and in my opinion, the comics were generally better quality than what we see today. Scott Snyder's Justice League likely would have been edited. "Your story is taking way too long to tell. It's this never ending thing, and it's not even particularly compelling most of the time. You should have wrapped this stuff up a long time ago, so we can focus on other things and other characters." I would tell him something like that if I was editing his book. Actually...I'd probably just fire him off the book, but that's me
That's another thing, too. You've got to be on the hunt for good stories. That's number 1. That comes even before pandering to big name creators, in my book. Snyder isn't delivering a good enough story, in my view. It's had some bright points, but overall, it's kinda' boring to me, and the sales aren't really strong, relatively speaking.