I would argue that none of these characters is interested in justice. Antonio is totally defeatist at the trial and just seems to accept his fate. Perhaps he is so resigned to the inevitable loss of Bassanio that he doesn't care about very much any more. Portia offers Shylock terms that seem reasonable and even seems urgently to want him to accept them but when he refuses she is draconian in her judgement and Shylock is utterly ruined. I think her priority is just to get this messy situation sorted out as soon as possible - preferably by throwing money at it - and to get back to her fairytale world in Belmont with her new husband Bassanio. Shylock certainly seems interested only in revenge for the cruel abuse he has received at the hands of the so-called Christians in the past. There is no denying he has been abused by them - Antonia admits it and we also see if for ourselves in several scenes - so we can see some justice in his case but he seems blind to any kind of compromise or settlement and seems literally to want blood. It is hard to see Jessica as anything other than a party girl, carried away by her love affair with Lorenzo and by the lively social scene of Venice. She does not give her doomed father a second thought or backward glance as she joins the party returning to Belmont. If she showed interest in either justice or revenge we might think better of her but she is just too superficial to be bothered by such deep issues.