See, this is why I've maintained that if it wasn't Pina it would eventually have been somebody. He was always going to betray Remi because he's the kind pathetic mediocre dude who reacts to his own inadequacies by trying to drag others down. He wants to be flattered into thinking he's something he's not.
Remilia is clearly way more badass and cool than Angel and he reacted by becoming the realm's most powerful wife guy in less than 24 hours of knowing her. Now that's a real one.
That's the point. He's weak. They all are weak. It's like in a Persona game. Initially, your party members are going to be weak, petty, etc until they find their inner strength to deal with the world ending threat. Pina wasn't good enough to build them. All she did was flirt, sleep around, spend money, and not deal with fighting. You know, what she's supposed to be doing. She's supposed to become strong enough to take on gods with Will. Yet she's just petering around doing nothing. I mean, let's say... start game Chie from Persona 4. Initially she's pretty selfish and self serving, even going so far as to manipulate her best friend into needing her, and do you think if she didn't find her inner strength and level up, she'd stand a chance against the final bosses? No. She'd get wasted. That's what happened here. Will and his boys ARE weak. They ARE petty. They ARE inadequate. They should have had their crisis event so they could become better people, become strong enough to go up against gods trying to end the world, but at this point? No.
Look at Persona characters at the beginning, compared to how they end up at the end of the game. They go from selfish to selfless. Ready to lay down their lives for the greater good going up against a god as opposed to whatever they were spending their lives on initially. EXACTLY what happened here.
Pina was just a bad FeMC. She wasn't good enough to become the leader that she should have been. She had to use items to lure people to her, to get on her side. And she didn't do anything but spend money and sleep around. As a result, Will and the rest of the party members are still stuck at essentially level 1. They are nothing now.
Yes, Will and his boys suck, but they are also victims of Pina messing up the story/fate. If Remilia didn't do anything, I doubt Pina would have. She was just not interested in going out and saving the world.