That always felt like a stupid retcon, though.
The original concept behind Durotar was that it was reflective of Draenor, before Draenor turned into a super diverse continent of various clumped ecosystems for gameplay purposes rather than a planet with one tileset we knew the orc clans to be associated with. That combined with the timing of Medivh showing up and there being no other environment to go to that wouldn't have been unsustainable for occupation with an extremely scattershot Horde at the time due to pushback from the humans or other environments.
Then we went 3 installments of WoW with no criticism or critique or issue of the living situation other than the requisite "we need to kill 10 quillboars" that every zone has in terms of pushback/expansionism.
The whole "we need X and Y!" didn't really show up until they needed reason for Garrosh to be angry at the Alliance and have youthful orc support beyond "Alex Afrasiabi wanted war back and Metzen wanted a Thrall foil."
Retcons are retcons, and it's still technically true and a huge fumble now, but it always felt super out of character with the Thrall we saw in Founding of Durotar, who was prone to mercy but also wasn't a damn throwrug. It's as silly as "there's food lines in Westfall but Horde settlements pop up in 40 seconds." Fight for the world's diminished resources, indeed, trailer voice.
EDIT: OK, 2.5 installments of WoW. Stuff like Glory did come up. But beyond that, it never felt like it was the intention when it was created as an environment to be in. Founding of Durotar framed the entire thing as a triumphant, successful exodus (that had to happen to stop the Legion in RoC anyway).
Kind of obnoxious how it felt very hamfisted just to have a reason to stay pissed off. They could've come up with myriad other reasons for conflict that didn't frame Thrall as a total failure when the intention (by the writers) is for him to not be anyway. It's one of those awkward disconnects between narrative intent and reality.