Then we have to clear up the differences of the limits between TTRPGs and and other media.
I suggest a possible solution, it isn't almost a retcon. The ordinary Athasian halfligns don't eat sentient beings, and the meneater "halflings" have got a different name, the jerrens. Maybe these are worshippers of some Lovecraftian entity, and also with some tainted biotech gadgets.
* We shouldn't waste our time about certain details because these can be easily omited or changed, in the same way they have been in Ravenloft. Maybe this has been the intention by WotC since the begining, in the first moment.
* Maybe the creation of the muls wasn't by means of forced breeding but by remains of transgenic engineering by the rhulisti biotechnology.
* Could sentient Athasian spiders the "oddparents" of the Athasian drows?
* Could be possible "biohackers" in DS? Could life-shaped creations to be used in the circus arena for "pokemon battles"? Couldn't that technology to be used for renewable energy sources?
Could alchemy be used for (preserver) arcane-magic effects?
* Could any plants to survive the defiler magic, but mutating into any thing like the brown tide, or the Martian red weed (from War of the Worlds)?
* What if special plants from the "Endless night"(Shadowfeel) could survive in the Deadlands, and this used by sentient undeads to become "sentient shadowtouched plants", to live again? They could breed again and rebuild the civilitation.
* What if other zones of Athas have been invaded by efreeti from the Fire elemental plane? And these have to defend their conquered zones against raids from the infernal planes. (Doesn't this sound very heavy metal?).
Can metal be mined from the Earth elemental plane?