What's the bar, though? If out of a million people reading a joke, 80% find it funny, 20% find it meh, and one solitary person needs the joke explained to them, I think it's still fair to call it a funny joke. There are multiple comments in this thread missing the satire so it's obvious the percentage is a bit higher than that, but I'd wager the majority of people didn't need the joke explained to them.