I dislike Yukine as much as the next person but, and a huge but on that, his unbearable behavior is understandable as pointed out by
@iztia. I blame both Yato and Yukine for how things turn out to be, but the person who is at most fault, in reality, is just father. He put a stop on Hiyori, the only person who could maintain the rift in the relationship of the trio from breaking apart, ironically the most flawed character, a human being. I'm pretty sure father will have a sad backstory to live up to his hatred towards the Gods but it won't redeem all the shit he has done throughout all those eras. Fuck father, but I agree that the Gods are a bunch of self-centered assholes who want to maintain their status and are too coward to accept that humans won't worship the same deities forever. Deities are born and die as time goes by and things change, just like any other being in existence.
This just shows that no one in the story is truly only evil or just good, everyone in this is flawed, especially the so all-mighty Gods.