Look at it this way: Modernism did this experiment of eschewing the past, of establishing a year zero. That was about as successful as any other religious force that denied that we had antecedents.
Look at it this way: you have just arrived at a football stadium, but you have no song to sing because nothing has existed before. It has really, but suddenly it's all disallowed. You have no history. It's not going to be that great an experience. Postmodernism is the huge laughter from that assembled crowd when they realised that no one even had a song. That laughter became the song. That *is* postmodernism. And yes, it's all echoes now.
The Grand Narratives of religion and belief and State were our hypnotics, our song losing or winning.
One day we awoke. But really we wanted to sleep some more. We didn't like being awake. Now we build Dutch/Hanoverian sinovial brick turrets that people call 'Lego buildings.' Some of us are still larfing ourselves sick on the terraces at the entire structuralism of post-structuralism. Oh, I mean postmodernism. Oh, I mean toothpaste.
Dan Brown didn't arrive fully formed from Hell. He was courted and solicited. Regard him as the post-postmodern throwback to the primordial firelight. He didn't just cough up Roslyn Chapel; you asked for it.