It's hard for me to dislike the villains in the Magnus Chase series, because the "dishonourable dead" is a meaningless phrase. Sure, it can mean evil people. But it can also mean people who just weren't deemed "righteous enough." That could be any of us. If you don't perform a suitably valorous act, you go join Hela in Helheim. And like… Helheim actually sounds fine. It sounds better than the Fields of Asphodel or the Fields of Punishment. But I understand and fully sympathize with all the abandoned and dishonoured dead, because they just want to find a place in the sun.
They're heading off to war with Loki and Hel and the giants, because they were abandoned by the gods themselves. It really feels like Ragnarok is just a virtuous thing that needs to happen. The Norse Gods haven't done good by many people in these books. Loki was suffering and finally earned freedom. Unlike with Luke in Percy Jackson (where I felt his reactions to the gods was completely unjustified), I fully understand the perspective of the people aboard Naglfar. That Rick Riordan wants to make them the big villians of the story makes me feel super conflicted, honestly.