I’ll go even further and say that, while not as immediate in its direct impact on American culture, the release of Rapper’s Delight (RD) was as momental an occasion as the Beatles on Ed Sullivan.
Musically, the 20 years after the release of RD, we watched as rap wrested control of the R&B form fully away from the-then giants of the field, the young white guitarists who used the blues structure to create songs about aliens (“Come Sail Away”), mystical crap (half of Led Zeppelin), and whatever it was that Jethro Tull and Yes were doing… whatever it was, it was blues-based but it sure as hell wasn’t the blues!
But rap? These rappers looked cool, sounded like they were intent on making money while having a great time while doing so, and banging all the hot chicks … I mean, what better toned message for the Reagan administration?
White guys? We were singing “we don’t need no education” and calling it art. (Again: no wonder “classic” rock died - the tone was completely anathemetical to the zeitgeist of the 80s, whereas Rap was right on the mark.)
And that brings me to the second point as to why this song is important… and to better understand my reasoning, it may be worth the time for the reader to listen to the 4th episode, by Wesley Morris, of the 1619 Podcast hosted by the NY Times.
Go ahead, I can wait. I need to pause my writing anyway. 
Done? Good.
So think of Rap as an extension of that, an extension of the cultural re-appropriation of Black culture by African Americans. Morris… knowing the audience he was trying to reach… started his story with Yacht Rock and then, eventually culminates his story with Motown, calling the founding of it “the most important event in the history of black music in America” for it represented the first time that black people owned a stake in black culture and made money selling that black culture in a truly capitalist fashion.
And he’s probably right, but the story didn’t stop there, did it? For at the same time Motown was flourishing, so was white R&B… in the form of Rock ‘n Roll… yet another example of cultural appropriation (look, people get mad that Led Zep “stole” Stairway, but the open theft of Muddy Waters’ style and riffs is called an “important development” in the history of RnR. Puh-leeze.)
Rapper’s Delight marked the next step, where the black artists… and not just the black entrepreneurs who hired black artists… would own their lives, their work, their material. They were going to make money and have a good time doing it!
So, now, in 2019, the musical world of 1979… the world the Beatles created… is dead. It has been replaced by a NYC subculture which first debuted in the mid-1970s and is highlighted, economically-speaking, by the amount of control which is held by the artists… which you can hear in this very song.
And that’s why it’s Pretty Damned Important.