Robert commented earlier on an item from Vulture asserting that NBC should thank fans for having kept Chuck alive.
Instead, I think Alan Sepinwall has the "who should be thanking who" cause and effect much better aligned.
And most of those shows [Parks and Recreation, Friday Night Lights, Community, Chuck, 30 Rock, Parenthood] get ratings that would get them canceled in a heartbeat on any other network. The thing that's made NBC an industry joke has also made it a place where a niche show like "Community" can hang around for at least two full seasons (and hopefully more), where there's now a better-than-even chance that "Chuck" might stick around for a FIFTH season, where they recognized the brilliance of "Friday Night Lights" enough to seek out that DirecTV deal that kept the show in existence for three extra years, where "30 Rock" will likely be around for as long as Tina Fey wants to keep doing it.
The contention that if NBC had its act together enough over the last several years to develop better rated new shows, that the collection of relatively poorly rated shows that have continued to exist on the network would instead all have been cancelled makes sense.
Although, if you were to argue that on another network some of those shows wouldn't have been so poorly rated I'd agree that makes some sense too.