In the UK, 75% of deaths are people aged 75 and older. I'm not sure if its the same age profile in the US but I would think yes. Even here in the Bay Area, the death rate is about 0.5% for everyone below the age of 60. If we lock down those over 60, and let everyone else live with masks and social distancing, the infection rate may skyrocket but the hospitalization and death rates will plummet. This is basically what we are seeing globally now, where the infection rate is higher than in March but death rates are much lower. Granted, there were less tests being run so that makes things hard to compare.
Also, the bigger problem is those that need to take care of their parents who are in this age group. The infectiousness is so high that if the children get sick, the parents will definitely get sick. So this is the biggest quagmire, that entire families will become isolated to protect the parents. It's not a perfect solution but better on a percentage basis for the entire country than locking down everyone, even though the risk profiles are drastically different.