I saw the matinee today and I think it's a show of great production value that works as entertainment but doesn't necessarily work as an adaptation--to the point where I wish they had just marketed it as "Gatsby-inspired" or something instead. While it still deals with some of the themes from the book like social class, the American Dream, etc., it feels like those themes take a backseat to the main love story (and side love stories) that plays out, to the point where all the tangled romantic threads seem to make it feel almost like a melodrama.
I think an issue with removing Nick as the narrator is also that they can't figure out how big of a character Nick should be. Because the whole book is told from his point of view, they seem loathe to make him "just another character" and actually end with his narration, but most of the time he just seems to be around to add a level of moral preaching to the story.
I thought it was a fundamental flaw that the music wasn't of the 20s era (though in the director's note, they mention that this is intentional to "bring the audience into active conversation with the present") and fwiw other friends I talked to didn't seem to have the same issue. But the music that is here feels very bland and generic contemporary musical theater. There are a lot of power ballads and high belting that get the audience excited but ultimately the songs don't go anywhere or otherwise feel too on the nose (Myrtle's numbers as well as the second act opener, Shady, were some of the best songs I thought). The orchestration flirts with jazz stylings occasionally before falling back into a standard musical theater pop (a la Mean Girls/Dear Evan Hansen).
Writing aside though, I think it's still a fairly enjoyable work, especially for those that just want a fun night out and don't have much attachment to the novel. The scenic design is absolutely gorgeous and does some good work in integrating projections to actual set elements, and it makes smart use of the pit as Gatsby's pool. And the music can be fun at times, if unmemorable.