Anniag brings it up when she mentions how Prince Attrebus saved a whole bunch of Argonians from slavery. Mere-Glim responds that they knew slavery under the old empire, too, meaning the current enslavement is happening in the post-Septim environment.
I wonder if maybe Morrowind came out of the Oblivion Crisis not much worse off than the Imperials. They still have their natural resources like Ebony and Glass, after all. After (and maybe during) the Oblivion Crisis, Helseth's main concern was probably holding his people together despite the conflict between Redoran/Indoril on the one hand and Dres/Hlaalu on the other.
I think Helseth is like Scotland's Robert the Bruce in some ways -- determined to be king even if he has to make deals with an empire (and kill rivals the way Robert the Bruce did), while at the same time genuinely concerned for his people and managing to keep an empire at arm's length. Helseth's situation at the end of the Oblivion Crisis would be as if England had imploded politically during Robert's reign, freeing him up to unify Scotland (Morrowind) even more. (Not that it did in real life, as far as I know.)
ThatOneGuy made a lot of good points though. I hope we learn more from the two upcoming Keyes novels.