Do the sums for yourself.
To let some people go back to normal means the virus runs through society quickly
Under the assumption that by back to normal you mean no NHS cancellations due to covid overload, then you would have to class as vulnerable anyone over age 45
Otherwise, the hospitals get full very quickly, whereupon death rates from everything also go up
What kind of normal do you think that will be? Shortage of teachers, shop assistants, dustbin men, doctors, all having to be protected
It doesn't work
And then there is the issue of the people over 45 who have to pay their bills, get their medicine, take the kids to school ...so the virus gets into your vulnerable population
It really really doesn't work