Yeah but then they just look like young people. Looking for an actor who conveys to the audience that the Emperor is old, while also looking young, really shortens the list of who you can cast. The priority should absolutely be whether an actor can be menacing, can emanate authority, ruthlessness, coolness, whatever qualities Denis is looking for in his version of the Emperor. That’s what helps the story, not stressing over a description from the book just for the sake of it, whenever it makes the role so much harder to cast.