In Consciousness Explained, Dennet is deliberately not dealing with that problem because he had already written his thesis, a book, and several papers on the subject of content and qualia and that sort of argument. He was also a student of Quine, who had his own rather extensive criticisms of the notion of intentionality and subjective experience. As such, he decided to leave that particular sort of discussion out, and just focus on his main objective (as he remarks in the appendix).

The following papers represent I think a pretty good summary of his response to the sort of objection you raise. They might not be the best, but they seem to be the ones that come to mind at least for me.

https://ase.tufts.edu/cogstud/dennett/papers/quinqual.htm

https://ase.tufts.edu/cogstud/dennett/papers/JCSarticle.pdf

The first is an extensive attack on the notion of qualia as a useful notion. The second explains the methodological approach implicit to rejecting this sort of notion, especially in the social/psychological sciences.