The "at risk" groups include a sizable percent of the US population, and isolating all of their first degree daily contacts alone is likely impossible.

Hospice patients, and the hospice workers.

People already in treatment, and the healthcare professionals providing them with care.

People who smoke, have diabetes, a heart condition, or are immune compromised, and so on, and everyone they know.

This has got to be millions and millions of people, and this isolation will be extraordinarily porous. Those folks have friends and family too, they will slip up, exposing their contacts and then the virus is on the other side of a firewall. And we've seen how quickly the virus spreads in isolated groups!

Which is not very realistic as a possibility given the number of people that fall into the at risk groups. It sounds simple in theory but seems very unlikely to be something workable in practice.

It's impossible to isolate only the at risk group. That's like 30% of the population. Also, there is growing evidence that even mild cases can leave more or less permanent damage.