I am in France and I have seen almost no negative effects of the lockdowns etc of the sort referred to here, things went back to normal pretty much as soon as schools returned and I rarely hear it talked about. The difference I think is that the lockdowns were much better organised in France, and information was far more cogent here, both info from the media and info from the government. It felt streamlined, better organised, more sensible and better informed. Rules were strict but not inhuman. The schools were very well organised, sending out weekly work by email and zooms available. Vaccinations were well organised and again the info was more streamlined. There seemed to be better organised social net arrangements - re children in need or businesses in trouble - I don't have personal experience but the information provided to everyone seemed very clear. Addresses by Macron were good. Feels like the good ol' days at the moment! In the UK, judging by the media and threads on MN, it seemed bonkers by comparison.
The long term consequences in france have been more to do with economic consequences. But this is also all affected by other factors which have happened since lockdown.
The problems which the UK faced I feel may have been to do with how the UK handled covid and how it handles education and governance generally. There seemed to be a lot of unnecessary confusion and incorrect information on the media. Schools in the UK at the time had pre-existing problems which did not exist in France at the time, and covid possibly was the tipping point. Parenting and expectations of parents in France is different from the UK too.
This is just my impression though.
I think next time no, we should not let oldies die. We should be better prepared earlier and listen to good science. We were being forewarned by good science in January, yet not much happened for months. Lockdown in itself was the right thing to do, the problem was not lockdown, or masks, but how it was organised.