I got the feeling that because it was so sudden after the Invincibles attack that most of the cities were still partially evacuated. Like, if I was a person in that world no way in hell I'd be in a metropolitan area after that shit for a while. I'd be with my family out in the bumfuck hills without even a McDonalds in an 30 minute drive.
It's also entirely possible that most places looked abandoned because the animators were lazy and only showed people when they needed frightened/dead civilians.
Hot take but I didn't think Jeffrey Dean Morgan really matched Conquests body. It felt slightly off. I think he might've been better for the Emperor or something else. Thought it could be slightly deeper.