Like I get it, I get they wanted to go with some sort of acceptance route, but the entire narrative leads up to a possible cure and solution. The way they ended it is a cheap cop-out for not being able to change or add in things in time for release. Yes, they're badasses in Avernus. But Avernus FUCKING SUCKS. And it's just throwing her back into hell.
And I LOVE that there's an acceptance arc for Karlach. It's so important, and something a resonate with a lot. I come from a background of childhood trauma, and had to go through a sort of acceptance arc of my own--accepting that what happened, happened, and I can't undo that--was huge for my growth as a person. But at times, I still felt I was "doomed by the narrative," in a sense. I can never be who I would have been without the trauma. I'll have to live with it forever.
I worked hard, and things got better for me. The fact that things got better does not, in any way, cheapen the importance of acceptance! I had accepted that I would live a difficult, isolated life--and now that I don't, I appreciate what I have so much more. And the work I did to accept and move on still guides me when I struggle. Fixing Karlach's heart doesn't mean her arc is wasted. I hope Larian sees that.
