The thing that astonishes me is that we really haven't made a dent in the problem.
It's surely something we've wondered about since prehistory, and since then we've made scientific discoveries about things we never even suspected existed. But we still don't know much more about consciousness, except for some additions to the chemical and physical events that can disrupt it.
Dennett's point, or at least the point he was trying to make 20 years ago, is that one of the reasons consciousness confuses us is that it isn't actually quite what we imagine it to be. Our visual experience seems continuous, but we know from eye saccade movements that it cannot be. The way we feel the passage of time seems very straightforward, but the 'cartesian theatre' fallacy shows that our brain by necessity can't be processing things in a specific order.
It's surely something we've wondered about since prehistory, and since then we've made scientific discoveries about things we never even suspected existed. But we still don't know much more about consciousness, except for some additions to the chemical and physical events that can disrupt it.