It's nice to see that Rationalists have reinvented Maimonidean virtue ethics. The idea that humans personality is maximally pliable, and this is metaethical grounding for the concept of moral responsibility is an extreme on a spectrum. It has some inspirational value, but I've never found it especially compelling.
Also, the fact that this article does not mention the Big Five once really makes me feel like the author is trying to reinvent the wheel but has never looked at a wheel before. Despite its flaws (and the broader methodological critiques you could level at personality science as a whole), it is the most scientifically grounded model of human temperament that we have right now. But why start with the latest science? That would involve leaving your bubble, which is a major no no.
Sorry for the snark, but this is scientific reasoning as cargo cult at its worst.