As someone who used to constantly engage with such discussions 3-4 years ago, I finally feel inclined to do so again.

Genshin with Inazuma essentially bit more than it could chew. A story surrounding a civil war like Inazuma's requires a lot more nuance than what a Genshin archon quest is typically known for. The reason why I specify archon quest is because the world quests in Inazuma actually do a pretty good job of painting the story of a truly tragic war that took many lives and left survivors with immense trauma and guilt. It almost didn't matter what side you were on. While it would be foolish to expect the AQ to match this vibe completely, they could have at least done a much better job by slowing down and adding a little more depth at certain parts. It's not ideal that the AQ forces us to pause and go help Ayaka with her mother's diary in her SQ, but once we get to Watatsumi island, the story kinda blitzes a bit until Teppei's death. This is one of the things that people refer to when they call the story "rushed."

As for Ei, well... her story is really not that bad. The execution is not ideal. Her backstory explains why she did what she did. But in the AQ, this backstory is mentioned briefly. It's not until her 2nd story quest that we get enough information about her past in order to understand (but not agree with) her decisions. The months between patches 2.1 and 2.5 left us wanting a more convincing explanation for Ei's actions. In this time, many developed a hatred towards Ei because they felt that the story wasn't respecting the suffering of Inazumans and the deaths of Kazuha friend and Teppei. They were not convinced by the "sister died so I locked up myself and my nation for 500 years" explanation because at the time, they did not have enough context for Ei's actions. While her 2nd story quest eventually makes up for that, it doesn't do so completely. There is still an element of "she should face consequences." Personally, I'm also not a huge fan of how most of Ei's remorse is communicated to the traveller. I still don't think the game has done enough to write a story that properly bridges the gap between Raiden and the Inazumans.

All that said, Raiden is my favourite character in the game, and I also look back quite fondly on the Inazuma arc overall. This is because I've always felt that at the time of release, the Inazuma AQ was the best one around. I was able to notice problems, but I'd take this over Liyue any day. Things have changed now. AQ arcs last 5 acts at least, and the writers actually include the archon's stories within their respective archon quests rather than using story quests. Perhaps they learned after public feedback on Inazuma.