My zombie horde that I have are not Lego brand, either, and I've got a couple of space sets that are "Brick Master" or something like that. In both cases, as you've indicated, they're not as good quality, but they're fun. The zombie horde is fun, but cheap. Kinda fitting.
That's the thing, if Lego aren't going to produce the sets people want they'll go elsewhere. I'll certainly by more Sluban for sure, but will keep it separate from the Lego stuff.