Like "Dinosaurs on a Spaceship", I think this can be seen as an all-out pastiche of an earlier era of the show, in this case not the first one but the immediate previous one. This is a heartfelt tribute to Davies-era Earth-invasion stories (right down to Trinity Wells the American news presenter making what I believe was her first appearance in the Moffat era). Unfortunately I like it less than "Dinosaurs" as it seems to accidentally or deliberately point out just how formulaic the Davies-era Earth-invasion story actually was. (Much more than the UNIT era, which despite its formulaic reputation has I think only about two or three pure simplistic aliens-invade-Earth-to-conquer stories - "Spearhead From Space", "Terror of the Autons", and possibly "The Claws of Axos".)