The whole business environment has changed and Australian airlines are simply going the same way as other industries.
You wouldn't set up a business manufacturing cheap electrical goods in Australia anymore as no matter how well you did you would be undercut by the Chinese.
The same with textiles, Bangladesh, Vietnam and China would always be cheaper.
The car makers are pulling out as well because of the small local market and high costs. It's cheaper to produce in South Korea or Thailand and ship the finished product here.
QANTAS can only compete on a select few international routes where it doesn't go up against competitors who offer a superior product at a lower price. As a high cost, end of the line operator with a long history of mismanagement and a strongly unionised workforce it won't fly against the modern hub airlines operating new fuel efficient aircraft from a lower cost base with no unions, competent management and an aviation friendly government.
At best QANTAS could be a small boutique airline along the lines of Air New Zealand if it got it's house in order.