That's not the full quote:
"We're all zombies. Nobody is conscious - not in the systematically mysterious way that supports such doctrines as epiphenomenalism."
which is pretty important unless you want to misrepresent his view as a denial of consciousness, which it's not unless you accept qualia in general or in the epiphenomenal "side effect" sense. To provide a bit of background, if you were to study consciousness with the heterophenomenological approach (the one Dennett promotes in Consciousness Explained), there's nothing which tells you the "lights are on and someone is home" other than their reports, correlated physiological changes etc. If qualia (from the epiphenomenal account) are to have no function, arise from changes in our brains without themselves having a sort of measurable effect on other brain states (causally inert), then we cannot falsify them and so "we're all [empirically] zombies."
Dennett is a compatibilist. What did you mean by this, the typical libertarian free will?
He doesn't, his theory just attempts to avoid the "hard problems of consciousness" by explaining away the hard part. Consciousness is still a thing to be studied, otherwise his whole "heterophenomenology" would be pointless, no?