You are never past the point of lockdowns stopping it. It just takes 14 days of strict lockdowns and all the people who are currently infected without knowing it have progressed to either known or recovered.
Then you just do some testing and contact tracing (while remaining in lockdown) to mop up the rest of your infected population.
This applies to any infected population. Note that most lockdowns define "essential" too widely - beyond just supermarkets, doctors & hospitals.
The problem is you need to keep utilities running and hospitals open. Then there are slightly less strict lockdowns where people can get limited exercise outdoors, buy groceries, and food production continues. NSW tried this, and it's failing. I suspect it's a combination of delta is too contagious for lockdowns to work in practice, too many people will violate them, 14 days doesn't account for asymptomatic household spread, and 14 days is more like p95 than p999.
A further 14 days and any regions with no cases are safe to exit lockdown, as long as you have good border controls.
But I imagine that if your hospitals are flooded with patients and Covid is rocking your area, you need those initial 14 days just to reduce the caseload to the point where you can test and contact trace again. That's all it takes to get back from "impossible to eliminate" to "we just need to stamp this out now"