One of the worst movies I've ever seen.
My one star up there is purely out of generosity. This film is a frenetic mess filled with over-the-top (and gross) scenes. We get it, they were hedonistic in Hollywood (and I'm sure, still are), but we don't need 3 hours of reminding.
The movie is pointless and never draws you in. You're left watching it from a distance, with no chance of connecting with any of the characters.
The reason it's one of the worst movies I've seen in my life is because Chazelle put so much into it, except his heart. It's over-the-top and just spectacle. It definitely had some potential. One of the biggest problems was the casting of Diego Calva (Manny). He's so off the mark as this wide-eyed young man trying to break into Hollywood and 'falling in love' in the process (not at all convincing). Toby McGuire is decent and Margot Robbie is good, but everybody else sucks.
This movie is so bad that Chazelle should never work again (Heaven's Gate and Waterworld come to mind).