My one big complaint about the Ravnica book is the portrayal of several of the guilds as flat antagonists. This is a pretty severe flanderization of their portrayal in the first Ravnica block. I quit magic before return to ravnica, so its possible this isn't the D&D book's fault, but it really fails to capture why some of the guilds exist in the first place, the useful functions they actually serve that the city relies on.
Orzhov is, or at least was, the primary religion of the setting, most people worshipped at orzhov churches and dealt with orzhov banks, even those of other guilds. The Orzhov banks aren't just a racket, they provide a needed service that keeps commerce flowing between all the guilds. The religious services are even more important - Ravnica doesn't have an afterlife. Souls don't /go/ anywhere when someone dies. With orzhov, those souls are collected and put to rest - or to work. Without the Orzhov, the streets of Ravnica would be overwhelmed by confused angry spirits within a generation. Yes, a bank that traps people in debt forces their ghost to work it off after they die sounds pretty evil and oppressive - but *something* has to be done with that ghost, and letting people work off their debts in the afterlife means that poor don't have to suffer under that debt during their life, and working off debt as a ghost is hardly all that different from burning away sins in a pergatory type situation. None of the afterlife management nor the legitimate banking services offered by the Orzhov come across in the Ravnica book, and not seeing the needed services the Orzhov provide makes it much harder than it should be to see now good or even non-evil Orzhov characters could work.
Yes, the leaders of the guild are super corrupt - they're both bank managers and the leaders of a massive organized religion - the ambition required to rise to such a position generally doesn't go hand in hand with compassion, and even if it did that much power tends to corrupt even those who weren't corrupt to start. But it's not hard to envision compassionate faith leaders who tend to the poor and sick in a church led by power hungry lords, and you can have good accountants and financial advisors who actually help people manage their finances and achieve their goals in a bank owned by heartless predatory plutocrats, and good people working in the Orzhov guild shouldn't feel any more strange.
Similar with the Golgari. At least their sewage treatment and corpse disposal roles are mentioned in the book, but not their farming. The fancy rooftop gardens of the Selesnya provide high quality food to the wealthy, but not nearly enough to feed the teeming poor. The golgari's great subterranean fungal forests, the same forests that break down the waste of the city above - also provide the staple diet for the bulk of those living above. Again, it's not hard to envision good farmers even if they're forced to work with or for an evil corporation like Monsanto, and it's not hard to envision good garbage disposal workers even if they're working for a corrupt government official.