https://www.smartraveller.gov.au/COVID-19/leaving-Australia
There's a ban on overseas travel from Australia. If you're an Australian citizen or permanent resident, you can't leave Australia unless you get an exemption to travel or you're travelling to a destination that's exempt from the ban. Foreign citizens are able to depart Australia at any time.
Australia is the only Western country which has an exit ban on citizens. There are so many people who got rejected and can't leave Australia despite having dual citizenship.
The whole situation made me reconsider applying for PR and moving to Canada instead.