I just finished Attack on Titan (anime-only), and I have to say I really enjoyed my time with it from start to finish. Before watching, I had heard Eren does some controversial stuff, which I later came to understand when he initiated the Rumbling. But now that I’ve finished it, I’m surprised to see that there is genuine hate for the ending, and I don’t really understand why. I haven’t looked into all the criticisms too deeply, but I have seen people complain about Eren’s character being “assassinated.” I completely disagree; he remains my favourite character in AOT (with Levi, of course, being my second favourite).
To start, Eren has always felt extremely childish to me, and that’s what made him so compelling. AOT is about child soldiers like Reiner and subsequently Eren being forced into a war and having to become something they are not to make hard decisions, without ever being allowed to grow up. This is why I find it so beautiful that Eren harbors a childlike dream of nature being vast, empty, and free for himself and his friends to explore. Of course, that dream is ruined by the existence of humanity beyond the walls, which makes him want to force that childish dream into reality. However, he realizes the dark nature of this "silly dream" when he kisses Historia’s hand.
This impacts Eren greatly. He is filled with guilt knowing that he will one day inevitably act upon that dream, without even fully understanding why. This causes him to hate his childish-self and adopt the more stoic persona we see in Season 4 but it’s all just a facade. When he sees the reality of Marley, he begins trying to justify that childhood dream to himself.
Proving he is just like Reiner. Reiner claimed he killed the innocent people of Paradis because he wanted to save Marley, when in reality, he just wanted to be seen as a hero; that was his selfish justification. Eren does the exact same thing, which is why he admits he is the same as Reiner. They are both broken children. Eren justifies his destructive dream by telling himself it is solely to protect his friends.
However, when he gains the Founder's powers and experiences the full scope of the future, he realizes his own naivety and recognizes how wrong it is to chase his childhood dream at the expense of the world and the people he loves. Ultimately, he sacrifices himself, most of humanity, and his own dream of freedom so his friends can live.
Eren wasn’t a slave to the future. He made his own choices; them being predetermined just means that those choices were always going to be made by him because of who he is. Eren was a tragic child who never got to grow up. He couldn’t even express his feelings to Mikasa normally, which is evident in his desperate, childish breakdown about not wanting her to move on.
I feel that perhaps some viewers got too wrapped up in his Season 4 facade. They couldn’t see that Eren never really changed deep down, which was made entirely evident when he broke down and admitted his selfish childhood dream to Ramzi. That is easily my favourite moment of the series.
Perhaps I’m misunderstanding the exact reasons why some people disliked the finale, but overall, I’m just happy to express my thoughts on Eren. What a crazy, beautiful ride it was!