I found the article was heavily focused on simply the nostalgia of the movie without really looking into the plot or character motivation. I would agree the movie would be a "Great White Hope" narrative if the plot was about saving jazz, but it isn't. The story makes it crystal clear that although love Sebasian and Mia have for these old art forms is admirable; it is not sustainable without some sort of compromise. John Legend's character is never a villain or an adversary he ends up being completely right about how to succeed in an age where Jazz is forgotten because people are dying out.
La La Land is about the love story with these two people and how their lives are affected by the way they view their passions over their trust for one another. As I reiterate, the second half of the film is critically to breaking the traditions of the movie being another Golden Age Hollywood homage. Not to mention the article neglects the diversity shown during the dances, backgrounds, and settings of the film and an interracial marriage that is a thread throughout the movie.
I offer this video by Satchel Drake as a counter-arguement.