When there is a sudden demand for an export product and production needs to ramp up quickly to take advantage then we miss out if our companies don't have the extra workers needed.
So we need
1. A pool of trained unemployed Australians to take up the slack
OR
2. We need to quickly import trained workers.
We can't afford to wait around years for current Australians to become available and be trained.
If you don't like the idea of a pool of unemployed Australians you need to look at imports. You can't have it both ways.