With Fire Emblem, I think there’s a lot of context that folks don’t apply to Edelgard, which leads to an incomplete look at her character. I often find that folks say, “She’s evil in 3-4 routes” as if it means anything.
War is also seen as “an ultimate evil” yet historically, major change in the world comes from major economic downturns...or war. Nobody else is willing to stand up to Rhea and the authority of the Church. While certain things Edelgard was told were not true, and that she could be called misguided, the point stands that Rhea, and thereby the Church, were effectively oppressing the continent, not allowing it to move forward, and perpetuated a system in which suffering was often brushed under the rug.
Do I agree with Edelgards actions entirely? No. But considering her hands were tied (TWSITD spies in monastery, can’t trust classmates to not freak out at the idea of war...literally think about the reaction a lot of fans give), diplomacy with Rhea was never an option. It sounds nice in concept, but it’s not applicable to the story and isn’t realistic.
I haven’t played Blue Lions. I will at some point. But Golden Deer, while clarifying why Rhea did certain things, did nothing to convince me that Rhea was not a problem. There are simply things I cannot agree with when it comes to leadership, and while religion in itself isn’t a bad thing, having a religious leader abusing their power/position, allowing particular things to happen under their watch, and the system itself with the Monastery and the “school which is also run by the church” makes me question things.
As they say, “All is fair in love and war”. I also think the conversation isn’t as black and white as folks make it out to be. Everything changes depending on the path you take in the game, so theoretically they’re all valid in particular ways.