I respectfully disagree. Astarion is finally happy with who he is, finally accepted that he's enough.
He has made no indication he has a desire to return to human life. He wants to be free and also wants to walk in the sun.
You fixed the first issue by killing Cazador.
The questline for a nonascended Astarion is that he discovers he's enough and worthwhile exactly as he is -even as a vampire spawn.
He wants the ability to walk in the sun as a vampire spawn.
A cure is not the answer. It's not even something he has ever indicated he wanted.
Curing him of vampirism would be a solution that gives him the freedom to walk in the sun, but at the cost of changing who/what he is.
It's counter productive to everything you spent the game teaching/telling him.
In the graveyard, he has embraced his circumstances and his life. He says goodbye to the memory of his former human self. The one who 'lay here, dead and buried'
He can be a vampire spawn and find a way to acquire a sunwalking ability or find an item that grants it.
A cure isn't necessary and isn't inherently the answer because it fixes the sun problem.
Well, for starters the possibility of a cure has Never been even mention in the game, so it is logical that he is not expressing any opinion on that. He does, however, voices a lot of drawbacks of being a vampire throughout the game. After killing Casador without him he tells you that you've doomed him to an eternity of hunger in the shadows. He tells the Gurs that the pain from hunger alone is unbearable. Plus intolerance to water and sun, and other little encoviniences along with being hunted for being a vampire. Sure, Ulma tells him that he will never be hunted again, but a few hundred years from now noone will remember that.
As for the cure, as of right now the only possibility to escape the misery of being a vampire in BG3 is ascension. I do not know why there is no other option even mentioned anywhere, wish spell/true resurrection. I think that Larian either didn't think it through or just didn't bother with it.
But anyways, I think the option for the cure should be presented in the final conversation. It is a small and easy fix for Larian to add to make a lot of people happy.
IMHO his whole story arc is about getting his body autonomy and self-respect back. Stop seeing himself as a tool for others to use, stop being "slave" literally and figuratively. Learn how to stand his ground and be a wholesome person just the way he is. And our JOURNEY to get him there is WONDERFUL until you get to the ENDGAME. And then, well, the finale is very lackluster to say the least. Starting with a childish cruel joke at the docks and then very shallow final conversation. It is a conversation between two pals not partners/lovers, standing 10 feet away and having a light chat lasting 1 minute...
