The reason why the alternative would not work, as shielding the vulnerable and those at harm does mean locking up 15 million+ of the pop anyway, it's lockdown just another kind of lock-down and a permanent one until Covid is eliminated. There are just too many people that fall into that category, as you can tell by the vaccine priorities.
Lockdown 1 was needed, but it was botched completely, we never went on the Covid elimination strategy meaning 1 and a half months of harsh lock-down 1 and closed borders for good meaning by now we would be completely free, yes we are not quite an Island, thanks to our land border with Ireland but I am sure we could have negotiated with Ireland to do the same. (the gov appear to be doing the closed border part now, only took them a year!)
So I am pissed off that a 3rd nevermind a second but a 3rd lockdown was needed. Up here where I live, we have effectively been in lock-down since October! No end in sight either, because this is such woolly lock-down, it's taking ages to get the numbers down, rather than going hard and fast and getting the damn thing over with, this lock-down the way it's being managed is almost completely ineffective, we are lucky infection rates are coming down as quickly as they are (and that's bloody slow). Meaning people who are currently obeying the rules like me and have already not gone caving for months, have to spend longer not doing the sport they love and not being able to see tier parents/family, mates in the pubs etc. You can see why I (and others) am starting to think feck-it, no one else is obeying/laws are too woolly anyway so I am not even sure I have to obey them as its not a legal requirement anyway. So why should we continue to give up what we love, because this government is so incompetent, while others are able to get on with their lives?