Your only option is to engage with in-universe systems. There a lot of failings of the D&D alignments mixing with IRL morality. You can disagree only as much as your god belief allows you to which, as demonstrated, can vary wildly. This is assuming you want to disagree within the game. If you as an IRL player don't care then you really can only go with kill or ignore.
I think this is where I have a profound issue, because the game is approaching the idea of redemption from a very specific IRL cultural/religious perspective. But since I don't come from that particular religious tradition, I am having great difficulty accepting it.
From my experience with BG3 EA I think it's fair to say the game will provide us with several paths leading to different outcomes. For example I believe that with Shadowheart we will get a chance to turn her away from Shar (which could be interpreted as a "redemption" of sorts but a Sharran would simply call this "betrayal") OR to sabotage her secret mission causing her to become hostile towards us OR to help her with her evil mission confirming her as a Sharran making her fully and completely evil.
Okay, but for me this is insufficient (a weakness of the game's writing), because a more reasonable path (for me) would be turning SH away from Shar but then making her truly pay for any and all evil she's done (i.e. atonement without any reward for the atonement).
