How many brand new franchises not based on anything can you name in the last few years? Despite endless complaints about remakes and sequels audiences are terribly resistant to new ideas. And it's not like Paul Feig hasn't done original films in the past, he's done Bridesmaids, The Heat and Spy (and like Kristen Wiig has thus far resisted the temptation to just do a sequel to Bridesmaids) so he's probably at least earned the right to be a bit lazier this time.
And to the person saying one character is like a walking stereotype, maybe we should wait to see more than thirty seconds of footage to judge that?