I can kind of sympathize with the difficulty the Forgotten Realms setting imposes on writers, especially if you're trying to have a tragic ending. I've DMed quite a few tabletop D&D games over the years, and one thing I always do is tell the players that, in my game, magic to raise the dead is not available casually or easily. If you're bringing someone back from the dead at all, it'll be a whole quest to achieve it. I do this because the ability to raise the dead messes with the ability to tell an interesting story- it's very hard to have a meaningful threat of death in a universe where your surviving friends can just pay a cleric to bring you back in a few days. Sort of like how time travel can totally remove any stakes from a story if you handle it badly. The thing is though, within the context of BG3 specifically, the dead absolutely can be raised. There's even funny dialog from killing companions and then bringing them back. So when you take my character that has a scroll of True Resurrection in their pocket, who is themselves a cleric with the ability to call on the direct intervention of a god once, and then insist that no, actually there's simply no way to help my friend in desperate need, and give zero reason why I can't use any of the tools at my disposal that should absolutely work- that feels extremely arbitrary. On the other hand, as I think I've said before, I can absolutely get why something like the divine intervention ability isn't used this way- having to write around the player having a one-time "resolve this quest" button would be an absolute nightmare- but it doesn't change the frustration of being told "no, you can't do that" with zero reason why you can't. (Well, actually you don't get told that, you just never get the option at all, but you know what I mean)
