And considering where I saw it was mostly people our age, I can't imagine we were the only ones.
No major movie could ever draw in a large enough audience by appealing to just one demographic, so it's not an either-or question. The goal is to include a range of aspects that will appeal to multiple different audiences, that will draw them in for a variety of reasons. Of course it drew in a lot of younger Batman fans, and the reunion of Burton and Keaton probably drew in the Beetlejuice fans, but it also relied quite heavily on Jack Nicholson's and Kim Basinger's star power to draw in the people who weren't comic book fans. That's the whole reason for casting a big star like Nicholson or Marlon Brando in a movie like that, back when comics and sci-fi were a niche genre without the mainstream appeal and respectability they have today.
(See also: George Lucas casting Sir Alec Guinness and Peter Cushing in his obscure little space fantasy movie starring three unknowns and a couple of robots.)