I am GenX so I can speak from my personal experience, which I realize is not universal.

I actually bought "Rappers Delight" on a 45 rpm single the year it was released. But it's also true that Blondie's "Rapture" was the first rapping song I heard on the radio. I would have been 13 at the time and rap was far from a mainstream musical style.

Looking back now there certainly were specific individuals of GenX and Jones who had access to rap, but it was certainly not available to me as a suburban kid in Canada. Even that Sugarhill Gang single was hard to find because "rap" as a concept didn't really exist at that point. I am trying to find a recording of the Extras song "Hip Hop Hip Hip" as an example but it's so obscure neither YouTube nor my streaming service seem to have it available. It would be unrecognizable to you as hip hop because nobody knew what hip hop was then. People were experimenting broadly and some of those experiments are now considered part of the movement. But we didn't know that then. Another example that stands out for me was "White Lines" by Grandmaster Flash. It was largely spoken word and I would have identified it as funk then. Now I guess I don't know.

"Straight Outta Compton" came out when I was in university. I really liked it because of the anger. The raw emotion felt like the best of the punk movement from 15 years before.

So yeah I could have been clearer. The early seeds of what we now consider "rap" were around when I was young. But I would not have called it a popular genre in my circles, or even mainstream. I don't remember rap shows in the clubs (and I spent a lot of time there in my teens and twenties).