Yeah, making the ghosts scary would be missing the point. They were never meant to be horror movies, but rather, they were lampooning them. Making the ghosts scary would just lower the accessibility of the franchise. And then there's the idea of toys, which means they want this to be accessible to children.
With so much time having taken place since the second movie, I'm kind of nervous. So much has changed since those movies, and a lot of it has to do with the different faster paced blockbusters out there now.