Maybe there is some truth to that. The golden age of movies for me was those great years when I was able to go see (on average) three movies a week -- the stuff I watched as a kid, and then as a teenager, and then as a college student. Those are the experiences that still shape my tastes today, that still stand as the movies to which I compare the films I see now.
It doesn't seem too long ago, but back then movies were cheaper and my friends and I would flock to practically every new release. If we liked a movie, we would go see it multiple times.
And when you're young, there's nothing that competes with dinner and a movie as a simple, perfect date.
Hollywood continues to make movies for "kids" because they arguably have more leisure time than adults with 9-to-5 Monday-through-Friday year-round careers, weeknight and weekend family obligations, and only limited vacation time. Younger people arguably have more discretionary income than adults with mortgages and their kids' tuitions to worry about. Young folks are more attracted to going to the theater for the "social scene" whereas adults would rather spend their time building and enjoying a home entertainment center.
Also, in this age of social networks, wireless/portable media, and content overload, there are countless ways to market to young moviegoers, so dinosaurs like me are easily forgotten.
With so much more media competition nowadays, ticket prices are up and the young demographic is still a gold mine of opportunity.
Don't mistake my cynicism as a complete rejection of the Hollywood movie experience. I still love film, and I still believe that great movies are made. But the moneymakers in the entertainment industry have their eyes set on a bigger audience that, unfortunately, I may no longer be a part.