The Australian dollar is valuable because you can buy lots of things with it (but not only, see below).
The Venezuelan bolivar is not valuable because you cannot buy anything valuable with it.
That’s it.
That’s what a currency is.
A currency is only as good as what it can buy.
The day the Australian economy collapses will be the day the Australian dollar will lose its value.
The day the Venezuelan economy starts producing valuable stuff again will be the day the Venezuelan bolivar will be valuable again.