According to the CDC in the US, if you have a negative test on Day 7, the chance of you spreading Covid-19 is about 5%. After 10 days of quarantine with no test and no symptoms, it is about 1%.
Covid-19 quarantine periods can be as short as seven to 10 days for some people, the CDC advised Wednesday, but a 14-day quarantine after coronavirus exposure remains the safest option.
edition.cnn.com
Obviously it depends on risk - if the Australian government wanted 0 risk, that isn't possible. The current hotel quarantine program is as close to 0 risk as possible, however, clearly, the economy is suffering.
I don't understand why they don't look at shorter quarantine periods. Or why not look at a 'trial period' of 2 - 3 months. See what the effects of a shorter quarantine period (in hotels, with a negative test) is.
A 7 or even 10 day quarantine would make a huge difference to the economy. More passengers can enter the country, giving stranded Australians more of a chance to get back home sooner.
If they continue this 0-risk policy, Australia won't really open up till 2022/2023 or even longer, because vaccines are going to take up to a year for other countries in the world to bring down the numbers significantly - if that is possible.