People love dark themes, I mean, look at scare mazes, they're berely intense at all, you probably go a max of 2mph, there's not banking, berely any height variant yet people flock to them.
In all seriousness though I think people labelling Thirteen as a failure of marketing are missing the point here. Those pre-teen kids are pretty fearless. I've taken a seen plenty of kids under 1.4 at alton trying to drag their parents onto Oblivion or The Smiler. They're reaching that age where they want to tell their school mates of the scary rollercoaster they rode on their summer holidays. When I was there, every single day I had to deal with a guest who's child was too small for Galactica or Nemesis, I could always say "but there is a big rollercoaster you CAN go on!" and point them to Thirteen. That way the family still felt like they were getting their money's worth (to an extent) it was a useful tool in diffusing the situation.
I don't expect SW8 to be groundbreaking on the world stage by any means, but I'm very excited to ride it. I've grown very fond on re-ridable family coasters that make me giggle all the way round over rides that make me almost pass out/throw up. It may be packaged as the next Nemesis, but who cares, it gives the kids a chance to feel like they've ridden a Nemesis equivilent.