I mean come on, you don't have to explain why it sucks, it's like Prometheus, just take our word for it that it sucks. For fuck's sake man; Pig slaves? Funny accents? Something reeks of mediocrity. *tips fedora*
The Doctor reveals himself from a crowd of three people and helps his friends break out of the Dalek lab, they escape to the surface in order to defend Burger Town from an impending attack from the Daleks which proceed to massacre their asses. After Solomon attempts to negotiate with the Daleks with a sappy ass speech cut right out of a /fit/ motivational poster, the Daleks shoot Solomon dead. Though according to Dalek Thay, Solomon was assaulting him with a skittle shaped knife and suspiciously hanging around the neighborhood. Dalek Sec, at odds with his newly acquired empathy, calls off the attack and captures the Doctor.
Dalek Sec reveals his plan to implant hollow human bodies with the Dalek factor using the Empire State Building as a conductor for solar lighting, and blah blah blah, it makes more sense than the Earth spaceship plan. After expressing an interest in humanising the Hybrids, the Cult of Skaro turn against Sec and convert the hybrids into pure Dalek soldiers. In order to contaminate the hybrids, the Doctor grabs the mast of the Empire State Building, so that his DNA can travel through the lighting and into the Dalek/humans beneath the building and blah blah blah, it makes more sense than the Daleks getting killed by a theme park ride. The Cult of Skaro execute Dalek Sec and the hybrids. Now aware of their disgust, the Dalek humans rebel against the Daleks, shooting them to death with Dalek tommy guns, then Dalek Caan suddenly remembers that he can kill them telepathically. After a last desperate attempt by the Doctor to offer the last Dalek a peaceful existence, Dalek Caan teleports and escapes.
Luckily, the Doctor is able to rescue Lazlow the Pig-Man using the vast resources of the Dalek laboratory, allowing him to live a full and happy life as a hideously deformed homeless pig-man in New York at the height of the depression, which is still a happier ending than a little girl growing up with the hate the Daleks put in her mind.
While this is easily the worst RTD Dalek story, it still somehow manages to get far more flack than it actually deserves because "muh penis-headed Dalek!" Yeah, like Classic Who and even Moffat Who monsters look much better...
The writer of the episode apparently bawwed her eyes out after the backlash of criticism, I don't know how credible this fact is, but it is hilarious if true.