A hasty generalisation. True of the ALP and the Libs, perhaps, but certainly not of some minor parties.
May I remind you that some political parties are actively attempting to implement radical change in society for better or worse.
You suggest that the institution of the political party is what holds back societal development, but this conclusion is a bit of a red herring. In fact, this lack of change that you speak of would appear to be due to conservative forces in society, whether they exist in a political party or any other institution. And yes, the 'big two' parties do represent this conservative force because they have a stake in the established order and so on, but this does not denote some terrible flaw in modern politics: they have a right to be represented
One other question: on what premise is radical change a carry-all measure of societal advancement?
Finally, yes: I would (in fact, will) join a political party, but not the Libs or ALP.