I'll elaborate.
At this current moment in time, for probably the next decade only the Coalition or Labor will have the ability to form an outright majority in the House of Reps. If you want to have a say in the direction out country takes, what policies we enact and laws we pass it is best to have some affiliation with either party.
Both parties are essentially the same in regards to policy, with the only major difference being in regard to workplace relations. Yet the legacy of Labor, due largely to Whitlam demonstrates that if you are in favour of a progressive Australia, the Labor party accommodates you.
If either party policies are of offence to you then by all means joins anyone of the other parties or become apathetic about Australia's future. Majority of people my age have zero interest in politics and think all parties are liars and corrupt. Yet I have the sense of knowledge to know that if I want to try and make the government better for myself and others then membership/advocacy for either Labor or Liberal is necessary.