This is absolutely astounding.
1. Did you miss all the care home scandals ?
Nope - but I suspect that the scandals are only a tiny percentage of the care homes. So you're advocating do nothing because of a tiny percentage of care homes have problems?
2. Do you really think that the vast majority of over 65's / 70's are in care homes ?
A substantial percentage of the over 70's are in hospital wards, nursing or care homes. And even larger percentage is in sheltered housing - like my mother. My parents downsized and moved into a retirement flat when their house got too big to look after. To get into the block where the retirement flat is, I need a key; access there is controlled as well - although not as much as for care homes or hospital wards.
Are you advocating doing nothing for all over 70's because some don't live in accommodation where access can be restricted?
3. There is still too many unknowns with people who are asymptomatic.
Are you advocating doing nothing because the problem is not yet fully understood?
You have just provided a perfect example why so many of the over 70's died. Every one of your points above is a reason not to do something. You can't protect all over 70's - but you can better protect the substantial percentage who are in accommodation/places where access can be controlled. And doing something about that percentage is better than wringing your hands and screeching "nothing can be done". Most of the over 70's are scared $hitless about Covid 19. They would welcome more active measures to protect them.