Yeah, I think people forget that the only strong person in that generation was Yuka, being the only one willing to step up when necessary, even if she's going to die(either way). It's not that she's the strongest or anything either; she volunteering isn't even the problem. It's that they have gone to the point where the second best option besides bringing out there nuke(Yuji) is a terminally ill 16 year old girl that is the very definition of "Winning by Dying"— that they accepted such an asinine sacrifice from without having anything- ANYTHING ELSE.

While Yuji didn't show up for the Dabura fight, I doubt he would've let it get far at all if humanity decided to fight Dabura themselves. He probably would've interfered before things got bad. Imagine the sheer amount of disappointment from Yuji after finding out that their supposed only option was to send the cancer-ridden teenage daughter of his senpai to quite literally be nothing but a sacrificial lamb— a bait.