NBC in particular is in desperate need of a brand identity. Lightweight sci fi isn't going to cut it. The networks in general show too little imagination and guts considering the dire straits they are facing.
People know what to expect from CBS, CW, USA, HBO, AMC and FX. ABC also has a reasonably strong identity, and FOX is burnishing its identity after allowing it to languish a bit, but what kind of show is an NBC show (and no the correct answer should not be "a total failure.") They really need to figure that out before continuing to flail around.
It's really not a question of quality. Some of the big cable hits lately, like American Horror Story and The Walking Dead, are far from uniformly praised. But shows like that can't be ignored. Bland broadcast drivel is far too easily ignored.