I didn't really find the story bleak myself. But then again, I like bleak, so maybe it's just a matter of degree.
Personally, I never grew up being taught a history that denounced indigenous culture as unworthy of mention and I've never really encountered any version of history that indicated this. Even in primary school, studying indigenous history and culture was mandatory and I'm not exactly a spring chicken. I'll have to ask my mother what she learned as she was a History major in her time.
Certainly there has been a shift from words such as 'colonisation' and 'settlement' to words such as 'invasion' and that has changed the light with which we now view that history, but this could well be an example of how history is just as much a mirror of the time in which it is written as to the time to which it applies.
One of the things I liked about
The Secret River is that I didn't really sense that. I felt that she gave me a context with which to view events that provided more than just a projection of some enculturated guilt.
It had its limitations as an exploration because you couldn't get much of a feel of the experience of the indigenous people at that time. I thought Grenville attempted to expose some of this through Blackwood and Herring and even through a few thoughts from the Thornhills themselves. But what I thought was more interesting than her attempt was her failure. I think it's absolutely crucial in the understanding of this story. Blackwood's advice is always too cryptic and Herring's blunt but without enough detail for Thornhill to make the connection. His own attempts at direct communication always frustrated. And as a reader, we feel that frustration, especially with our contemporary eyes.
To me the story is less about what was morally right and wrong and more about the danger of misunderstanding - of ignorance. The refuse of England was dumped on Australian shores. In my reading of this story, they were ill-equipped except in the minority to deal with an indigenous population and the kinds of events that occurred had a certain inevitability to them.
Of course, one might argue that the necessary understanding is still not here in the present.