Thats the thing though. How many times in real life do relationships where one party tries to change another adult's entire world view actually work? They very seldom do. Astarion going through with the ritual is something that his entire character arc leads up to, he hasn't changed at all. Caring for you doesn't change his world view. I would hate for him to become a Wyll like, that to me is a horrible idea. Nor do I want a more humane and sweeter character. I'm not particularly evil in my playthroughs but neither am I 'sweet' . If I think of Astarion throughout the game, 'Sweet' is not anything that comes to mind either rofl, adorable sometimes yes but not Sweet (and when he is its usually him being manipulative). I very much prefer him as a competent self assured and independent character who loves me and want to be with me in a relationship that is playful and fun rather than someone who needs me and clearly isn't independent. The game itself treats Spawn Astarion as in need of protection (horrible dialogue) good grief why would I want that for him?
Yes, and in real life, if you love someone, you love them for who they are, you like their whole character and even those traits that other people may not like. You may wish that he would be happier and enjoy life more, but not that he would "become a different person". The same mechanisms for emotions to arise and manifest are at work in the game, which is why those players who love Astarion are so bad at the idea of "fixing" him. Of course, it's impossible to want to see a loved one as dependent and in need of protection. It turns out that for such players there is only one single option left - Ascension and no other path is simply not provided.