There is not that much use to saying today, we should have done XYZ and the government was dumb to do otherwise.
We each have far more information about this virus today than what the government knew in March 2020. Given the lag between infection and death, and the lack of available COVID19 tests back then, for all we knew at the time of the first lockdown, the Infection Fatality Ratio (IFR) could have been 2%, 3% or even 5%. Now it looks like probably a still-high but much lower 0.5% to 1.0% with the best available treatment, but we just did not know that at the time.
Even with this benefit of hindsight, it seems likely to me that the number of COVID19 deaths would have been at least 2x higher, and quite possibly 4x higher, had we not had any lockdowns. Importantly, the 0.5% to 1.0% IFR is the death rate without the NHS having been completely overwhelmed across the system, even if it came pretty close. The IFR could easily have gone much higher than where it ended up if hospitals had been forced to turn away COVID19 patients who did not need ventilation, but "only" needed oxygen, steroids, anticoagulants, careful monitoring, and treatment of secondary infections, in order to survive the disease.
Finally, this is all ignoring long-term health effects other than death. Had all of us, or even half of us gotten exposed to COVID19 before having any vaccines available, it is quite possible we'd now have several million people in the population suffering from serious long-term ill health including, but not limited to, damage to lungs, hearts and brains.
So my personal view is, yes the lockdowns had a very large cost, but they also brought some very large benefits in the form of deaths and harms avoided. Despite all of the errors, the politicisation, the entitled misbehaviour by certain government officials, etc. it actually possible that at a high level, with quite a large dose of luck, this was handled more or less correctly, with a few critical errors that probably cost tens of thousands of lives, but also with a few good decisions that probably saved hundreds of thousands if not more.
Now that the worst is (I believe) behind us in the UK, however, it is time to continue to accelerate the vaccine rollouts and booster campaigns, and also to provide substantial support to people and communities who were worst affected by the disease and its "remedy" aka lockdowns. This needs to happen both inside the UK and outside of the UK.