There are many reasons why carriers aren't a good idea. The cost of an off the shelf carrier strike force is perhaps $70 Billion with a running cost of 3-4 billion/year. Plus you need nuclear vessels including submarines. Mostly though carriers are more for projecting power.
The US is the only nation running credible classic carriers. The US is a unique case given their propensity to collect allies and foes in large numbers by the carrot-and-stick method.
Australia, like most other nations, can operate from unsinkable land bases to defend its sovereignty.