At the beginning the lockdown was about not overwhelming the NHS. There was a belief that we had high-quality treatments for covid-19 (including ventilation) and that if too many people became ill at once this high-quality treatment would have to be rationed, leading to avoidable deaths.
One thing that's become apparent is that we don't have high quality treatment for severe late-stage cases of the virus. Ventilation is something worth trying as a last resort, for patients strong enough, but it usually fails.
Another thing that's become apparent is that it should be fairly easy for the NHS to predict, on the basis of medical records, who is likely to become seriously ill.
We could have tried much harder to treat people with pre-existing conditions in the first week of symptoms, testing, making sure their oxygen levels, pulse and fever were checked, keeping an eye out for clotting issues, and possibly prescribing hydroxychloroquine. Early action might have reduced mortality rates substantially, as it did in Germany and, actually, in Wuhan.
The advice about staying at home until you're turning blue should only have applied to people under (say) 60 and without pre-existing health conditions.
215 people under the age of 60 (1020 in total) with no pre-existing condition have died of covid-19. So unless you're very old, if you have symptoms and know you have no pre-existing health conditions, you'll almost certainly be fine. If you have a pre-existing condition the chance of dying is much much higher: 4 times higher in people under 40. 27 times higher in people over 80.
Because there has been so little focus on differential treatment, so little willingness to see early-stage patients, and because people in care homes have been neglected, our mortality rate is terrible. I now see no point in continuing lockdown without a sensible set of treatment and confinement strategies.
Among other things, the government could have issued every household in the country with an accurate thermometer and vitamin D supplements... We could have had corona taxis as in Germany in hard-hit densely populated areas. There's been very little intelligence about the way in which sick people are assessed and treated.