I see a lot of discussion about the themes of AoT in this last arc especially because people have come to expect a lot of dark gritty "war is hell", tragedy, politics & human ugliness & believe that's what AoT but it really has always been a greater story about humanity & life.
In the beginning there was humanity fighting against the titans, a representation of a "cruel world", fighting for their right to live and be free. Then there was fighting against their own oppressive government, then war among humans and now to end that same "cruel world".
Only now there is the alliance as well, a representation of humanity putting aside grudges, personal hatred, nationalism, prejudice to fight together, because we're all humans living in this world, and this is a fight for life itself.
It's a lot like A Song of Ice and Fire in that regard. Yeah there is the politics and warring factions but the ultimate point of the story is to put that aside and unite against the greater problem of the White Walkers and army of the dead threatening to turn that all to nothing.
But why defend this cruel world? Eren wants to destroy it to protect only those he loves, his own people, seeing no other way while the alliance fights despite life's suffering because it's also beautiful
When Eren's mother was eaten he regretted not appreciating the humble happiness he had before he lost it. Hannes also always said he'd give anything to get back that tranquil peace they had.
I think back to the iconic moment where Carla says "He's already great, because he was born into this world." The story has been telling us life is something inherently worth fighting for, and that's a good point for the new chapter to come in.
Zeke has believed that life is suffering and that there is no greater punishment than to be born, and now in this chapter he's accepted death & dismisses the alliance's fight as a byproduct of their inherently meaningless reproductive impulses.
And he says that being rid of our fear and the drive to multiply via death might be true freedom. Armin's response to is very simple but very true. There are small beauties to life that aren't motivated by "multiplication", there is a deeper drive inside us to protect life.
I mentioned it before but one of the core repeating ideas in AoT has been "the world is cruel, yet extremely beautiful". I think this is why Mikasa plays such a vital role, because Eren only ever saw the cruel part, unlike Mikasa.
Eren believes all he can do is "fight" so to say, do anything he can to destroy the "enemy" whether it's the titans that attacked them that day, the nation that wants to erase them, or the flow of the world itself. It's a "dog eat dog" world & everyone can only trample underfoot.
He knows he's no better than everyone else, that's why he tells Reiner "I'm the same as you", but if he has to exterminate the threat to protect what he loves, and there is no escaping that cycle, he'll crush his "enemy" so thoroughly there will be nothing left to ever retaliate.
You could say that to Eren "we're all the same" is his reason for why he needs to do anything in his power for him & his, while to Armin "we're all the same" is exactly the reason you cant crush others to protect your own, as Zeke exemplifies here even he has a memory to protect.
It's very profound for the most nihilistic character in the story, who parallels Eren in the belief that the cycle of the world needs to be stopped, in his case via allowing Eldians to quietly die out, would find a reason to stay in the world even for a moment longer.
I'm not sure where to really take it from here so I'll stop and go to sleep, but I think it's sad how much people on here have built this idea to themselves that AoT is a story purely about moral ambiguity, grim realism, tragedy & nothing else. It deserves a lot more examination.