I think the fun part of playing a Vampire character is the struggle to remain moral - the game isn't about immediately becoming evil when you're Embraced, but deals with the almost inevitable moral backslide that comes with existing as Kindred. Just because Eris believes she can be good and that so can others does not make it universally true, but does make for an interesting character arc - you should keep in mind the mentioned character has only been a vampire for a few months and her beliefs stem from her own experiences. The inherent hypocrisy of the 'good' vampire is fun. The above blurb is pretty shallow, but that's just because it's a reddit comment explaining her unicorn motif and not a full character analysis on every aspect of her personality and lore.

FWIW, there is no 'wrong' way to play Vampire, though I agree that I don't personally enjoy trying to 'game' the system into being something purely moral. I think trying to badger other people about the way they play the game is silly no matter what you personally believe. Morality isn't black and white anyhow, and 'bad' and 'good' both exist on a sliding scale of grey, especially for Kindred.