I'm going to get straight to the point because people had outlined all the plot armors, plot holes, and inconsistencies.

Since the beginning, Eren was driven by the pursuit of freedom. Whether it was freedom from the Titans terror or freedom from a hateful world, Eren did everything for its sake. The final chapter reveals that through the Paths, Eren planted the idea of “freedom” on himself the moment he was born. That being said, it’s safe to say that Eren’s idea of freedom is incredibly basic.

In Eren’s words from Chapter 121: “If someone tries to steal my freedom away, I won’t hesitate to take theirs.” Basically, Eren is willing to commit global genocide for his personal freedom. If Eren were depicted as the final villain, this would make sense as an antagonistic motivation. But since he’s Eldia’s savior, his myopic ideology is instead heroic and just.

A popular sentiment “Zeke’s plan results in the least amount of bloodshed, and is therefore superior to the Full Rumbling and the Alliance’s plan to stop Eren”.

This reminds me of an “obnoxious negative peace, in which the Negro passively accepted his unjust plight” described in Martin Luther King Jr’s Letter from a Birmingham Jail. Just replace “Negro” with “Eldian”. This particular peace would be espoused by those more devoted to “order” than to justice, who prefers a negative peace which is the absence of tension to a positive peace which is the presence of justice.

Now let’s talk about the Alliance and Yeagerist. People find it hard to sympathize with the Alliance because the setting is ridiculous and full of hypocrisy. Yes genocide is wrong. But the situation was clear that both sides (anti and pro the rumbling) were committing genocide indirectly.

People tells the message behind Attack on Titan is very realistic and not going to please some anime fans whom most are soft and can’t handle the truth of reality. They bitch and moans about how Paradis island ends up getting destroyed anyway and that all that blood spilled and sacrifice was for nothing. They can’t comprehend the message behind that about humanity in real life and how realistic something like that happening would be.

I understand the message behind Attack on Titan is humanity will always be a curse to itself and as long more than one lives on this planet, there will always be war. In short, many things aren't detailed which makes it ambiguous or raises a lot of questions.

[Summary]
My criticism is that Attack on Titan clearly promotes pro-genocide, both Zeke who wants the Eldian race to disappear, Eren who exterminates all his enemies, the Alliance and Yeagerist are the same at the end, and the inhabitants of the world who aren't calm before eradicating Ymir's descendants. Even so, seeing how bad the post timeskip narrative is makes it ruined masterpiece.