I don't even pay attention to time slots, the days where TV networks get to schedule when I watch their shows is long gone. Is Community in Big Bang's slot? I'm sure the NBC executives will take that into account come a renewal decision. They know they can't compete viewer for viewer with a big CBS show.
But they WANT to. If they have a show they think will be MORE appealing to a larger number of people, Community is gone.
NBC hasn't given UP (though, yeah, based on content, it seems to be so) in competing with the other networks.
The reality is they ARE in competition with other networks, time slots and ratings DO matter.