As much of a problem that it was, Canto Bight needs to stay as it is essential to Finn’s character arc in the film, and through the right trims and cuts I think it can be a lot better, like a quick mini-adventure. The only problem is that if you trim/cut the Fathiers too much, you will also need to remove the kids later on as the audience would have no exposure to them. If you keep the Fathiers but trim them, I think you should consider removing the kids. I think it hurts Finn and Rose’s characters if they free the slave animals and not the slave kids.

JEDIT: I think you should cut it so that they run into the casino to find the codebreaker and are arrested. They are in a hurry to find the codebreaker, they should not be taking their time.