I do agree with your points. But at a certain point a lockdown is the only working wavebreaker to release the pressure on NHS. It's certainly not a longterm solution but needed if NHS capacities are at a tipping point.It pulled down Austria's delta surge. It looks like their Omicron wave is starting now and that's with another set of restrictions in place. We know we can slow it down with lockdowns, we know we can "flatten the curve" if the controls are strong enough, they have to be a lot stronger than before to slow down omicron though and everything we've seen says it will return as soon as the controls are released. Unless we're talking about a lockdown until the other side of an omicron modified vaccine booster perhaps.
We don't know how to live with covid yet. I don't think the NHS has the resources to live with it. I can suggest a whole bunch of mitigations that could have prepared us better, from clean ventilation in schools, hospitality and workplaces to proper sick pay for people who need to isolate. But I don't think lockdowns offer a way out - a way of stalling it perhaps, but not a painless or easy option - which does mean the timing comes down to crude calculations about "what's the worst caseload we can handle." Which will vary from country to country and lots of calculations around vaccine coverage and number of people who can't go into work.
And make no mistake. From all the noises we hear here in Austria we will go into another lockdown soon enough because of Omicron. Seems this is our strategy going forward. If that's economically sensible is a different matter but short term it does release pressure on NHS and their capacities. To straight out dispute that effect (not you but the poster II quoted) is nonsense. It seems UK is going a different way though. Might lead to a quicker end of the Omicron wave but at big costs and the detriment of people working for the nhs.