Lore can be cool, but I actively embrace worldbuilding as a GM activity, so other than mining cool ideas, I much prefer rules to let me simulate my own world. Special mention goes to 4e's PoL, which featured a great way of writing its default setting that offered plenty of lore and flavor, but constructed it in a piecemeal way, where most of it was intentionally self-contained or only linked through implication, which left me as the GM an immense amount of room to worldbuild and curate which pieces they wanted to use-- as well as a convenient suite of 'fantasy land' elements to fall back on when I didn't want to overburden myself.