I've seen multiple spins on the scenario you've described, in which some scenarios the exhaustive approach is justified (the half-D world is on the verge of collapse, or about to fall to a corrupting force which will decay the resources, etc.);
is reasoned (if the protag leave the sustainable portion, their opponent or enemy will plunder the rest, basically 0-sum game);
is sustained (instead of harvesting everything, they transfer the resource to their own half-D, or if it's non-competitive, they do leave sustainable parts).
Then other genres of the wuxia and xianxia type where the protag is the leader of a faction, and have the faction resources (garden, mines, etc.).
I think you are thinking too deep into this. Reading a popular novel doesn't mean the readers agree with every action or idea the protag or the author take/presents, popular novel are more like fast food, maybe this fry is a bit too salty, maybe that fry is not salty enough, maybe the cola is lacking ice, etc.