To use a small example from your field which perhaps illustrate my point... It sounds to me as though, extending your logic, that one would say to somebody with motor neurone disease: "look, it's you that has motor neurone disease. It's not up to our government to assist you with paying for carers and providing medical care. Can't you go to university and come up with a cure for motor neurone disease? It's possible; look at Stephen Hawking!"
We have to help those people who have spinal injuries, at the same time as we work on safer motor vehicles, safer behaviours by humans, and motor neurone disease research, etc.
OP, Australia's resources are not limitless, neither the number of the world's less privileged Australia can accept as migrants.
Australia is borrowing money from overseas to fund overseas humanitarian missions.
Australia is selling off its assets and mines, its future income streams and potential to do good, to do good now.
If Australia got smart about doing the most good for the most number, we wouldn't be running down our future wealth and depriving ourselves of being in a strong position in the future to sustain the amount of good we might do.
My point then is, we must discriminate in what good we choose to do.
And the first point is to accept that we can't help everyone.
Regarding motor neurone disease
According to Access Economics' Migrant Fiscal Impact Model 2008, humanitarian migrants over a 20 year period are a net drain on Australian wealth, to the tune of $30,000 per migrant.
Is Australia better off using that money to accept 1 in 10,000,000 of the world's underprivileged, or to find a cure for motor neurone disease and banish it from all future generations forevermore?