Yeah.... ending itself is not nearly the biggest problem I had during my playthrough (looking at Orpheus and EMperor that we shall not delve any deeper here). I am also not opposed to having to make a hard choice at the end, but it does feel hollow due to clunky nature of the characters we are not to discuss here.
In my playthrough Karlach took the tenticle fall, and while I don't think it worked amazingly due to clunky set up, it also seemed like a decent ending to her as a character. Larian made a decision to completely screw over one character that isn't a piece of shit, and that's a narrative choice. To me the grimness of the ending can't be change through subtle tweaks, but it is a logical end point of a rather grim outlook that BG3 has as a game.
I am not sure how I will feel an another playthrough when I will have to sacrifice someone else that Karlach, but I also think that other characters necessarily deserve a happy ending (maybe aside of Laez, who seems to be more a product of her enviroment with a capacity of change).