Can you say for certain that in a future conflict that the ADF's MBTs and IFVs will be a waste of money and that the cheaper to acquire UASs and ATGWs will provide the needed capabilities?
I would look at it differently.
Australia is an Island nation.
Any circumstance where the Australian Government decides to use Tanks/IFVs will almost certainly mean they are deployed overseas.
In a foreign land supporting a Foreign Government or as an ally, say of the US, Uk etc
That will be a voluntary decision made by Government.
It is not a capability likely vital for the survival of the nation or defence of the nation.
It is a "nice to have" not a "need to have".
Unlike a fighter capability say, with the ability to attack aircraft or naval vessels approaching Australia.
4 Weeks ago I would have supported spending the tens of billions needed for 75 M1A2Cs and 388 IFVs.
Now I am not sure that whatever you want to achieve with that small fleet of armoured vehicles cannot be achieved in other ways for far less money.
Just my view.