Fiesco’s motivations can be a bit hard to follow as at one point he says that to throw away a diadem is divine, planning not to make himself Duke, but then the next scene he’s changed his mind.
Verrina’s last line is one of those typical wham lines that end a Schiller play- “I go to join Andreas.” Wait! You were the most ideological republican of the conspirators, and now, after Fiesco’s betrayal, which you knew was coming and avenged, you go over to the side of the autocrat? How does that make sense? Verrina is a pain, especially in his melodramatic imprisonment of the innocent Bertha to manipulate the other conspirators, but his politics make sense until that last line. It sounds like I’m complaining about that line, but really it makes you think and has an emotional impact and I think it would work on stage. It’s just hard to make sense of.
The scene (one of two variants, and the better of the pair) in which Bertha cross-dresses and goes out into the streets, rescuing herself, is fantastic, and the tragic consequences of Leonora’s similar action have a sickening inevitability.
Andreas Doria is a fascinating character, a magnanimous tyrant who disarms Fiesco by his refusal to react to his treachery, leaving himself open to whatever Fiesco does. I like that the play argues that tyranny is a problem even when the tyrant is basically a good ruler (not that Andreas will or can rein in his horrible heir).
The character of the Moor (referenced in Vasily Grossman’s Life and Fate) is cheerfully villainous in a Richard III way, with the humor coming from his incompetence. Fiesco casually uses him until he no longer needs him, then disposes of him (thus the Grossman reference) but this is complicated by the Moor’s betrayal of Fiesco at one point and Fiesco’s mercy then.
Pretty sure this review makes no sense unless you have read/are familiar with the play, but whatever. In conclusion, everyone should read Don Carlos, but if you like The Robbers, this is for you as well. I think this would work pretty well on stage.