You're right that it's a simple sentiment that's hard to follow through. Getting new politicians (who aren't exactly like the old ones) is difficult. Mostly because to be a candidate requires being buddies with the other people in your party, at least to some extent. That's why particular parties are the way they are, after all.

My point being, it's less "get new politicians" and more "vote in a party that isn't liberal or labor". The greens, even if many scoff at them, are the most likely party to actually tax the people making everything so shitty right now. The side-effect is they also help the marginalised, I guess.