People who complain about the story played this game with the butchered localization that made the characters inconsistent (the worst one has to be Xander). Some retarded, literal who youtubers then gave their opinions and blamed the writers, not the translators. There was then controversies with muh incest and muh gay conversion therapy so people who never played the games at all also started giving opinions. And on top of that the story is inspired by stories that are popular in Japan and Asia in general that aren't well known in the West, like the spider string, which makes the invisible kingdom being changed into some Ancient Greece parody utterly nonsensical when you see how Buddhism was a huge inspiration. The localizers tried to do that despite the final boss in Rev wearing a mask representing Buddha's face with no ambiguity whatsoever.

The mere fact that you say the plot is that Corrin and Azura conquer Hoshido specifically to prove that Garon is evil shows how even just changing some of Xander's lines ruined everything for everyone. They don't plan to actively wage war against Hoshido. They just go with the flow because they either obey Garon or get executed. The plot is pretty much "hey, since we're stuck in that shithole called Nohr and we're forced to invade Hoshido, we might as well try to exorcise Garon later". The Nohr siblings never, ever plan to stop Garon because while they don't want to go to war, they feel like they have to, it's their duty, and betraying Garon, their abusive father, would mean betraying the whole country and being executed by their batshit insane father. In the Japanese version, Xander never, EVER contradicts Garon or tells him to not kill people and to go easy on prisoners, he just shuts the fuck up, obeys, and hates himself for it. A lot of lines were added to make him seem like he actively wants to stop Garon because that's more marketable but he doesn't want to do anything at all.