I think Lamaros, what's being said there regarding Astarion, isn't that change in his character is bad writing, it's that the approval system i.e. playerreputation is a bad way of implementing relationships with characters, Astarion is a bad dude, but you can game the system to make him like your selfless pc, because...you said the right things to him or decided to kick a baby in front of him, once. I would also say that it isn't impossible to make a compelling narrative around Astarion like this but it requires you doing a lot of the narrative work yourself, but that could also just because of how little we've gotten so far
I think what is in the game so far doesn't necessarily follow that Astarions story is just linked to "is the PC good" and "does Astarion like the PC", but is linked to the actual interactions and decisions around Astarion. Assuming it's one thing or the other at this point is premature.
However, I assume they're less linked to the PC, given Larian's love of their origin character stories... but no one can really say.
And whatever way they do it it can also just be bad because the execution fails.
