Not all of us vote for the duopoly, but most very clearly do. Then of course you have the parties that you mentioned: One Nation, Family First, Gunlickers, Family First, Trumpet of Dickheads... who all deserve to be right at the bottom. The decent choices are very, very rare.
It’s hard. This was a conservative stronghold for decades.
The duopoly is a con, neither side ever loses, they just have to wait to be voted back in again. They play the long game, and play us for fools. It is the same in the US, except the people there get much more giddy when they see their favourite politicians wearing their favourite 'teams' colours.
A vote for Labor, is effectively a vote for the duopoly to stay in power. A vote for a decent party instead, at the very least pushes the duopoly in a decent direction, just as votes for right wing parties push the duopoly in that direction, which is their preferred direction anyway.
It seems worse now, one nation also made ground in the last election, while the ALP and the coalition joined forces to market against the Greens. I was born in 1974, Australia for me was very Labor party... until John 'children overboard' Howard came along, and I lost all sense of patriotism.