Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
This play has a bad attitude. Think about it: Coriolanus tells us that, in order to be a successful politician, you you have to be a big phony who's willing to pander for votes. The play's most successful political leaders (all aristocratic men) are manipulative and don't actually care about the Roman Citizens. But it's not just the political leaders who are flawed in this play. Shakespeare portrays the lower class voters as a fickle mob of ignorant, crude, and cowardly plebeians.
Harsh? Yep. Cynical? You bet.