Australia's emissions are small compared with those of China, USA, India, etc.  And it is quite true that if Australia is the only country to act it will hardly help at all.

But those countries have huge populations.  Would it make sense to say that each country should be allowed the same emissions, regardless of population?  Of course not!

Ultimately, every country needs to become carbon neutral anyway (or engage in some financial arrangement by which another country draws down what that country emits).

The countries which develop and adopt the required technology soonest will then be the best placed economically.  Meanwhile, does it make sense for Australia to take a lead?  Yes and no.  There will short term economic cost in going it alone, but this has to be balanced against the overwhelming need to encourage the others.  If each country waits for the others we all lose.