For a lack of better word, everything is over the top and not in a good way. If the director's intention was to show debauchery, recklessness, degeneracy and vices of the golden period of hollywood, when it was transitioning from silent to spoken, in the same vein as say Wolf of the Wall Street, then it has failed completely. Everything is shown excessively and without any substance. Story is nothing to write home about. By middle of the movie you would know how each character's arc is going to end. The performances are ok. Margot Robbie seems to be overacting. Brad Pitt is basically sleepwalking through the role. Diego Calva is good. After the stupendous First Man, it is a shame this is what Damien Chazelle has brought forth with all the budget he was afforded. Didnt like it much and 3 hrs were a slog.
P.S. - There is a nice set piece in the middle of the movie where a movie is being shot on a soundstage during the earlier days of spoken films. Now that was fun to watch.