That's kind of the problem tho. They DO have a personality and a voice and motivations and all that and it can be seen when you play as the other character. They aren't a blank slate, they are just completely stoic for the most part when you are playing.
This. You can't pretend to have blank slate protagonist if they make all their choices on their own. Your character in Astral Chains makes choices with zero input from you, they are a defined character yet the devs felt some odd need to make you a silent weirdo. How can anyone project themself into someone they have no control over? I can't make him be a bad cop.