Australian governments have been able to provide the substantial and very necessary fiscal support to the economy. It is also important to ask: what is the alternative? Absent the fiscal support, the Australian economy would be much weaker with the consequent economic and social damage. This would have materially worsened the fiscal position.
I don't see there is a trade-off between fiscal sustainability and fiscal support in the current circumstance. The cost of borrowing is at historically low levels for Australian governments. Borrowing costs are likely to remain very low for quite some time, and almost certainly until the economy is considerably stronger.