That's NOT a slipup. It's an artistic choice. Just because you disagree with it doesn't make it a slipup. By your reasoning, the fact that the movie wasn't set in the 1970s, no one wore '70s clothing or had '70s hairdos are also slipups.
I agree with Vice, why were there so many 80's references in the soundtracks? When you think about it, it makes sense. It was a popular 70's tv show, so it should have had more 70's music. The modern music made sense, because it was a modern Charlie's Angels, like Destiny's Child's songs, or Pink's "Feel Good Time" in Full Throttle, but what was it with the 80's kick.