The thing about Gabriel's death being pointless that tears me up is that it's LITERALLY a suicide. If it had been shot in a slightly less moronic way maybe it would look like him heroically sacrificing himself to give the Winchester's time, but as it stands, they literally just idley stood by while an extremely weakened Gabriel ran up to face Michael. Absolutely no shot.

Gabriel's trickster persona has always been a survival tactic. He chose to become someone who didn't need to face responsibility or destiny. He's not strong enough to deal with his family's fighting or to face them himself so he takes the easy road in life because it's easier for him to accept that he isn't part of the story than to believe that any of his choices matter. He kills people, and the fact that they're "bad" people probably has something to do with his resentment for Lucifer's corruption of humanity and serves as a way for him to manufacture moral superiority to other "monsters" but really he knows better. He kills people because he can. He's a low hitter and he'll find ways to hit even lower because trying to come up would force him to confront himself which is something he doesn't know how to do.

At some point, definitely the end of Unfinished Business, Gabriel does regret how he treated Sam and Dean, especially Sam. But he knows the things he's done are not the kind of things you can shrug and say "sorry bro" about. He abandoned heaven and by now nearly all the angels are dead. How is he supposed to face them? He's not a soldier and definitely not a leader. After what he's been through with Loki and Asmodeus, he's utterly sick of the Trickster path.

So what is there left for him to do?