It's a very simple argument. If you hold R_t under 1, the number of cases decreases exponentially. Eventually, you can unlock localities while restricting movement, and after some time the whole thing is dead in its tracks. This is something that almost every country eventually got around to doing anyways for probably longer on aggregate than it would have taken, it just wasn't timed right.
There is no need for digital mass surveillance to enforce a quarantine. It's been done before computers were invented.
Ooh! Oh we have to keep R_t under 1! Nobody thought of that. I wish the experts had spelled that out for us. Sorry to drip sarcasm but that is upsetting me.
How do you intend to achieve this miracle? Will the plan involve Maoist policies? How will the plan be hardened to prevent its being used for Maoist policies? Any mechanism that could possibly coordinate a worldwide lock-down of everyone is eventually going to be used to implement a "common sense" policy that starves ... these days it could be a billion people if coordinated globally. That is a much worse idea than the COVID pandemic which, apart from the lockdowns, was nowhere near as bad as a system that could allow global coordinated action to disable the world economy in coordinated fashion on demand.
COVID spread is an exponential process - you can't possibly do anything to stop R_t dropping below 1 from time to time. It saturates then recedes until a new variant appears. It it could possibly stay above one, we'd literally all have multiple cases of COVID right now. And I bet it does that fractally, so particular populations are all saturating and then seeing cases recede all the time.
The thing you're avoiding talking about seriously is the part that isn't already a certainty. Ie, the entire question.
R_t fell under 1 when the population was still naive. If you don't let the virus proliferate massively to begin with you won't have variants that are adapted to human immunity.
It's a certainty because it happened. R_t fell under one as a result of NPIs, not immunity.
You don't have to keep R_t under 1 forever. Just for long enough that the virus fizzles out. It's possible and in fact it has been done repeatedly.
There is no need for digital mass surveillance to enforce a quarantine. It's been done before computers were invented.