However, Rocket spent the five year gap after “the snap” either on Earth, or working alongside a number of humans from the planet.
For whatever reason, the space-travelling Star-Lord never visited home, so his knowledge of Earth always stopped there.
Peter Quill was kidnapped from Earth in the 1980s and he had a love of 1970s pop music instilled in him thanks to his mother.
Even if he spent most of his time in space with Nebula, where we first see him after the time jump in Avengers: Endgame, then, as Reddit user StarkReactor4 suggests, he almost certainly would have picked things up.