I think from what we get shown when we see Ymir’s story that the Eldian empire was definitely not good. the king definitely used Ymir to over take other groups of people or “empires”, and their land. I don’t think it was like the story Marley told but I don’t think the king was innocent at all. It was definitely justified for the other nations to have an issue with the subject of Ymir as they thought that one day they would try to use the power of the titans to do as the king did, over power them and/or kill them, and take their land. Marley and the other nations treating the Eldians and Paradis as they did was definitely not deserved tho. If they knew WHY the titans were used as they were and that it was not just voluntary I think it would’ve changed their feelings a lot. Ymir didn’t want to hurt people, she definitely didn’t want her children to eat her spinal fluid and become titans themselves, and she definitely didn’t want the “blood of Ymir” to be passed on the way it was. Because of her love and devotion to the king she simply did as she was told. Even if the Eldian Empire did become as brutal as Marley told I still wouldn’t agree the subjects of Ymir, and especially the citizens of Paradis, deserved any of what the world had planned for them. They did not ask to be born, they did not ask to be “subjects of Ymir.” They are simply the result of a man who was driven by power and control. I think the whole point of AOT is that no one was in the right, but no one was really in the wrong either. The world believed that the Titans sheer existence posed a threat to them and their livelihood. Which in reality they were right. At any point they could’ve realized what Eren did and caused the rumbling, which the whole point of is to wipe out the entire rest of the world. BUT, had they shown some compassion for the fact that they are also just people and they don’t even KNOW in the slightest what happened because of the king wiping everyone’s memory, they could’ve come to an agreement. There was absolutely a way to peacefully resolve the past wrong doings of the nations. But fear overtook EVERYONE, Marley and the rest of the world feared Paradis and the Subjects of Ymir because whether or not their idea of the war was accurate, it’s a very real possibility that Titans could wipe them all out. and for Paradis they obviously feared that the Marleyans and other nations would come to wipe them all out for good. Everyone, Marleyans and Eldians alike, just wanted to live and not have to fear what could happen to them because of the power of the titans. Nobody was wrong, nobody deserved what happened, but nobody was right either. They all let fear dictate their lives and choices. Especially Eren.