It might have been possible to contain the virus in late 2019 by locking down, but now it's too late. COVID is endemic and we have to learn to live with it. Some countries were hard hit early on, such as the UK and USA but they are now recovering as the population is becoming mostly vaccinated.
Some countries such as Thailand and Taiwan were largely spared up until recently but now they are seeing increasing numbers of cases, however the vaccine is now available so they shouldn't see mass deaths.
Zero cases isn't practical unless Australia is prepared to isolate itself permanently from the rest of the world and lock down for every single local case. The focus now needs to be on vaccinating and managing the opening up.