Same here. When you read through all of the background stuff Stirling worked up in the appendices, the Domination becomes a lot more believeable. I think a lot of people’s skepticism is rooted in the fact that that kind of society didn’t flourish here, in our timeline, so it couldn’t have been possible for it to have flourished anywhere, under any conditions.
We assume that we, as we are, are the inevitable and only outcome of history, and dismiss any alternatives, especially unpleasant ones.