Have you actually read the Great Barrington Declaration? If so, what is it about the actual content that you disagree with?
Or are you just trying to smear those who authored and support this policy (eminent medical professionals and epidemiologists) because they disagree with government and media dogma?
I'm getting pretty sick of this persistent "OMG the Great Barrington Declaration was sponsored by the AIER therefore must be evil" trope. If you disagree with the actual content, fair enough, make the argument, but attacking the people and the sponsors is just a cowardly way of dodging the actual subject matter by playing the "man instead of the ball", and smacks of having no actual coherent argument, instead a disturbing desire to shut down proper debate.
By the way, yes I have signed the Declaration.
On a first read through it would appear to have some merit, however if you are splitting the population 60/40 (as it's the case for the US, not sure how it would be split in the UK but probably not much different I'd guess as we've got an older population but probably better underlying heath) it's going to be very hard to ensure that those at higher risk are going to limit their movements.
For instance, with many grandparents providing childcare for their grandkids whilst their kids go to work, how would that work, given that their kids would the ones needing to go to work? It's not just work, in that they are likely to also babysit, so that would reduce the ability for the grown up children to go out as well. (It's not unlikely that grandparents can be 70+ whilst their grandchildren are under 10, essentially the grandparents have a child aged 31, which may not be their first child, who then have a child at 31, that child is then 8 when their grandparent turns 70).
Also there's a significant number of people who are workers who would fall into the older category. Even if they only work infrequently or a few days a week for pin/beer money. Which leads to the question what is the cut off age?
Over 70 then it may well work, other than you may still get significant numbers under 70 who still don't have underlying heath issues who could still get fairly I'll. Whilst over 60 leaves a gap between that and the state pension age and so you'd likely impact a lot more people who are in full time jobs. Even at state pension age not everyone wants to retire straight away (nor does every company want then to do so), especially if there's been some financial difficulty (including divorce) which may have had an impact on their quality of pension (also starting your pension later would give you a better level of income).
To clarify, I'm not saying that it's bad, just that I think that I'd need to know more details before I could comment fully.