That, and whenever one new sitcom becomes a particularly big hit, then all the other networks scramble to come out with their own knockoffs to compete with the hit. This dates back to the 60s actually: there was a point in time when monster and supernatural sitcoms dominated the airwaves: THE ADDAMS FAMILY, THE MUNSTERS, BEWITCHED, I DREAM OF JEANNIE, etc. More recently, THE OFFICE became a hit for some reason, so then practically every single new sitcom to follow afterwards ripped off THE OFFICE with that mockumentary format that really only works for movies and not TV: MODERN FAMILY, PARKS AND RECREATION, that Patricia Heaton show where all her kids got really weird names... I swear, it's so hard to tell any of these shows apart, because they all look the same.But anyway, back to the point. The reason why sitcoms seem unoriginal from time to time is that experimental sitcom formats kinda don't work out unless they're really really careful and lucky.
It was clear that WHITNEY was meant to be a female version of SEINFELD... nobody even liked the first season, so I don't know why it was renewed for a second season, but I do believe it finally got canceled.
NEW GIRL has become a big hit, despite that it too is a ripoff of another sitcom: TBS's MY BOYS, which pretty much is the same concept.
Heck, even when GLEE became popular, all of the sudden, musical series and movies became a dime-a-dozen.