You can also exercise your voice by... talking. That might mean trying to convince leadership, it might mean trying to coordinate a bunch of people who agree with you but don't want to act on their own, or, who knows, it might mean something else. But there are quite a lot of things you can do that are short of threatening to quit or simply leaving.
(And sometimes just leaving really is the best step!)
(And sometimes just leaving really is the best step!)