Eren’s attitude in chapter 90 is a clear contrast to the one we saw from him early on in the series. He still desires freedom but it seems as though he’s become much more… cynical about it?
He’s been through a lot since he made his pact with Armin to explore the outside world together. He watched in helpless horror as his mom was eaten. He declared a personal war against the titans, vowing to kill them all. He joined the military only to watch countless comrades be devoured. He discovered that he can turn into a titan himself. Many more comrades died for his sake. He discovered that not all of his friends are on his side. That some of them are, in fact, the enemy he seeks to destroy. He unlocks a power he didn’t know he had… only to later realize that it really wasn’t even him who did it. He starts to realize the issue isn’t as black and white as it seems as he learns that titans are humans, too. He learns that he ate his own father to obtain the titan power he now possesses. More people die over him. He hits an all-time low, begging to be eaten - to be released from this horrible agony he feels.
He almost loses his best friend, and abandons his commander - a man who helped him and fought for him countless times - in order to protect that friend. He knows that Armin still holds strong to his dreams, and that he had started to let his own slip away. He abandons some of his humanity to save his friend.
He starts seeing other people’s memories in bulk as he learns about his father’s life. He learns about Eldia and Marley, that they are stuck on an island, that the world beyond the walls is vast, filled with people, filled with conflict.
His enemy is no longer the titans. It is the Marley, who have turned his people into titans… and into weapons. As far as he’s aware, the whole world wants him dead. Suddenly… the titans seem like nothing. And they become nothing as they are chipped away one by one.
He reaches the ocean with his best friends, and they are so happy to be there. Armin has finally reached the staple of his dream, and Mikasa is there enjoying it almost just as much as him.
But Eren… he just stands there, looking across. He knows what’s on the other side. He’s seen it in his father’s and Kruger’s memories. He knows that he still isn’t free.
But it’s no longer about humans vs. titans. It’s about Eldia vs. the Marley. Or perhaps also likely… the world.
Eren has always cared about humanity, and has generally hated the thought of people dying (unless they are very horrible people, as Mikasa’s kidnappers were). The Marley are just humans too and Eren knows this. Even if they create titans, they aren’t titans. It’s not as black and white as he once thought.
He finally reaches the ocean, but he knows he still isn’t free. The ocean is no longer the endgame and so he doesn’t even spare a second to appreciate that they’ve made it one more step ahead.
He poses the question… “If we kill all of our enemies, will we finally be free?”
But it’s not that clear cut. Because he’s seen through other people’s memories that the same mistakes will always happen again and again as long as humanity continues on this path of war and carnage. Killing all of the Marley is no better than what the Marley have done to the Eldian people. Even Grisha found no delight in watching General Gross - the man responsible for his sister’s death - be torn away by a titan at the wall. Just as such, Eren likely would feel no delight in killing the Marleyan people.
Even if they could achieve freedom, does that really have to be the cost? What good is freedom if they must chip away at their own humanity and kill an entire race of people. Violence… War… It solves nothing. If the Marley people are killed, it can’t possibly give them freedom… Not with all of the blood staining their hands.
Freedom has become something that seems unattainable. Eren has never accepted that possibility though. Freedom has to be out there. That has always been his ideology. It has always been fuel for the fire. But he’s been broken down time and time again in order to achieve this one thing… And it’s so much further away than he once thought. It seems as though he’ll never reach it. He wanted the answers about the outside world… and he got them. And it wasn’t anything good. Not at all.
What more does he have to sacrifice to become free? Will he ever truly be free?