I know this post is like a month old, but I'm just reading through this conversation now.
I'm sorry but defending Scooby-Doo on the grounds of thematic depth, writing quality, and character development is just a patently ridiculous statement. As a fan of S-D, most of the Scooby media released across the past 40 years is really poorly written, has incredibly flat characters, and effectively zero thematic elements at all. It's an incredibly stale IP in all of those areas. That's fine actually! I believe the IP is still worthwhile despite that, and there are some very well-made exceptions to my statement, but using Scooby-Doo of all properties is a really flimsy glass house against FNAF.
It's okay to just say you don't like an IP and wouldn't be excited to see it at the event. Or that you wouldn't be a fan of the kinds of demographics the IP would bring in. No one has to justify that opinion with a bunch of poor arguments. It's already a valid statement.
FNAF is a long running, incredibly popular horror IP that fits really well into the jump-scare mold of HHN houses, has lots of merchandising potential, a Universal Studios-produced adaptation film that made a lot of money with a sequel on the way, that we know Universal tried and failed to acquire for the event as recently as this year. I believe it's hard to argue against the merits of the IP at this point.