What happened? Public libraries evolved to serve current needs. They've become vibrant learning centers, rather than old buildings full of books.
My pubic library has a few folks browsing shelves or reading quietly, but those aren't the majority of patrons. It's usually busy with students doing homework after school, oftentimes with the help of volunteer tutors. Adults take advantage of scheduled free legal clinics, income tax preparation assistance, baby & toddler storytimes, book clubs, adult (seated) yoga and chair exercise classes, Tai Chi classes, ESL classes and computer literacy classes, and so much more. Librarians help people fill out forms they find confusing. Various classes and lectures are typically held in conference rooms.
Very few go to the library these days with the sole intention of sitting and reading. Remember that commercial, "It's not your father's Oldsmobile?" Similar story. These are not the libraries of our youth. They're better, so much better. And so much more relevant to today's world.
I'd guess Marion would be thrilled at the changes.