Does Dogen bring good news? As I understand it, Dogen says that, at least for those new to seated meditation, there is no enlightenment outside seated meditation.

Well, to me that if true that's awful! No speech, no writing, no solidarity, etc.? I think it's this that is the stumbling block along the buddha way, for me.

Does it even have an answer?
One of Dogen's major teachings is 'practice and enlightenment are one' - what is important for Dogen is continuous effort in the dharma, and the basis of that effort is seated meditation. This applies to all practitioners, new and old alike.

Dogen tended to be disparaging of other schools, but if you want a less partisan Soto opinion you could read 'The teachings of Homeless Kodo' which acknowledges the value of other types of practice.