You're right mind you, there was indeed a golden period for our state, where other states had covid, and we didn't (we had interstate borders closed too). We had no restrictions and it felt like some kind of freedom utopia, like we had "won". But it was clear that it wasn't something that we could sustain for long. The community didn't want it to and eventually people have to move around again, to say nothing of required movements like transport and emergency health.

When we think about international travel, I think it's the same discussion. I do believe you that it's technically possible to have that level of containment, but I'm skeptical that it's possible at the scale that humans want to move about. The scale of travel is easy to underestimate, even mid-pandemic when the world was closed.

Australia only has a population of around 25 million, and in 2019, 4 million people flew in or out of Australia every month. In 2019 we moved close to the equivalent of the entire country across the border TWICE. For all of 2020 and 2021 it was still above 100,000 people per month, while we were locked down and international travel was banned, that's a lot of movements to get perfectly right to prevent a breach. Trying to scale that up to levels people are happy with is going to be really tough to get right. ( https://www.bitre.gov.au/statistics/aviation/international )

I think you're right that if a disease we decide is deadly enough comes along that we'll have no choice but to reduce throughput entirely, but at the moment I think you can reduce part of this discussion to a tradeoff we're making, between throughput and level of containment.