I know, which is exactly what i'm doing, it actually is a lot more fun to stay "in character", and thinking about a specific personality that you want to portray!
It's less about gameplay, i actually think SWTOR does a decent job in that regard, its more a point relating to visual design and athmosphere, and its actually far worse in the movies imo. Just look at Darth Sidious: he is a deranged, petty, giggling parody of a villain. You know that episode of Rebels where the Emperor talks to Ezra through his hologram? He looks like a benevolent, wise, powerful figure, not like some charicature straight out of a Tolkien movie. He seems almost diabolical, and - i a way - way "scarier" than the actual guy.
The Nazis were ****ed up, yes, but they didn't portray themselves this way! Thats why people got brainwashed, and believed that they actually were doing the right thing!
You know the movie "Jupiter Ascended"? Imagine that movie as a Star Wars movie, with the "Entitled" as Sith Lords.
Then compare that to the First Order, which is just a collection of edgy, angry kids, running around laughing maniacally.
Have the Sith be more like the Klingons, or the Roman Empire, and less about "me dark side, me evil, muahaha"
I dunno, maybe i just have a vivid imagination