2. Repetition
There aren't any new ideas anymore. It's true that most sitcoms are just rehashed versions of the last with just a few elements changed. As an audience we're used to this and we've grown to like it. But the same idea repeated in the same sitcom season after season? STOP IT NOW! It's the science research trip. For three of the six (completed) seasons, one of the characters has to take a trip away from California, leaving the others to 'deal with their absence'. The whole group went to the North Pole, leaving Penny behind missing Leonard. Then Howard went into space and left Bernadette (and Raj) to cope without him. And finally, Leonard went on the boat trip leaving Sheldon and Penny behind. Yes, each idea was good, well executed and propelled the storylines onwards, but there are so many other possibilities! If they need the characters to progress in their jobs, then Penny could get an acting job, someone could get fired or have to permanently relocate or someone could become a professor. All of these could inject humour or emotion into the show without ending each season on the very same cliff-hanger year after year, because let's be honest... 'how will they cope without their friend for a few months?' They're adults and they will be just fine.