Basically, Astarion's writer took this as an opportunity to impose some kind of morality message onto the player instead of letting the player roleplay how they want.

It's weird looking back at EA because everyone was like "this game is too geared towards evil" or "this game will have great evil paths." In the end, it ends up punishing evil paths and evil characters,
even evil characters from old games who could have been redeemed in those games.
(The spoiler is vague but just in case).

I can appreciate a theme or message in the writing, but I don't appreciate being given the illusion of choice in roleplaying and then being railroaded.

I'm not even an AA player, but I can sympathize with the frustration of those players, especially since everyone ends up patronizing them and telling them they're enjoying their fiction wrong.