The Big Bang Theory was only entertaining in its first season, back when it was more about science and competition to see who's the smarter physicist especially "Bat Jar" and "Jerusalem Duality" when Sheldon actually had fierce competition against other high-IQ scientists. Starting from Season 2, everything is about Love Love Love Romance! Instead of delving into quantum mechanics, thermodynamics and the size and dimensions of the universe, the TBBT has shifted on to kissing, dating, marriage, having babies, sex in bed, resisting the urge to commit premarital affairs, flirting and political correctness.
Starting from season 2, Penny got a bigger role and so the show shifted away from physics. Starting in season 4, Amy had to come in and despite the fact she's a neurobiologist she almost never talks about neurobiology her behavior is so stoic, colorless and stiff that she made the show even more boring. Amy is hands down the WORST character on the Big Bang Theory if not even the worst character ever made for a live-action sitCOM. What kind of sitcom inserts an emotionless girl without a sense of humor? The fact that the writers paired her up with my favorite character ever, Sheldon, made me even more upset and disappointed in the direction the show was going.