Drum hops on the thread:
Did adults abandon movies because movies got juvenile? Or did movies get juvenile because adults abanonded them? I've never come to a firm conclusion about this myself, but I suspect it's more the latter. As a social experience for dates, for hanging out with your friends, for getting out of the house movies are as good as they've ever been. And that's a big part of what kids want out of their pastimes. But adults? They mostly just want to relax with a bit of good entertainment, and they have a whole lot of other options for that these days. Options that, from an adult point of view, are generally superior.