Basically it went, "something something 'common putting the toys back in the box analogy' something something." I have no criticisms towards this train of thought as it's something I often appreciate in a writer, and I certainly don't blame Brubaker for the split just because if someone wanted to put them back together it wouldn't have taken a lot of effort on anyone's part. That their relationship is now in a state of constant questionability probably means it would have ended up this way regardless. I mean, you think they'd let Bucky and Natasha be a happy stable couple when they couldn't let Peter and MJ last? Marvel doesn't think functional relationships sell stories, and even a relationship centered around a history of brain washing and Russian espionage is too functional for them.