The problem is that Sam has always had the focus of the writers. He's gotten all the storylines, everything's been always about Sam's story. Whenever Dean got a storyline, it inevitably ended up being about Sam, but at least we had Dean's feelings. Now they've dropped even that. It's as if Dean no longer exists outside of Sam, and after the way they had Sam behaving like an asshole to Dean in s8 I just have no interest in Sam, not anymore.