People want to spend lots of time sharing photos of themselves and cats. Blame humans not Facebook.
How are people going to communicate and interact? Probably by sending text, images, and videos to each other...I'd love to hear some proposals for alternatives but I'm kind of tired of the "cat photo sharing" pejorative, because that's what people want, that's how they connect with each other, and if you can actually come up with a better idea you'll be very wealthy.