I can imagine an alternate reality where "bottom-up" playground settings were the norm, and "top-down" story-driven settings were deemed bizarre and unusable when somebody finally brought one out as a nostalgia item. D&D in this alternate reality would probably be a lot more fun.
As far as leaving the setting undeveloped on a low level so as not to restrict DM creativity, I think the objecters have failed to consider the hundreds (thousands?) of man hours that went into the Wilderlands box set's creation. If you think a lone DM under normal circumstances can create anything approaching that amount of material...well, you're being completely unrealistic.