I assume that you're talking about walling off people aged 60+ while the rest of us go about our lives? Unfortunately, that wouldn't work. Many people who are 60+ are still of working age - members of the Executive team and Board of Directors at my company are almost entirely of that age. My dad is over 60 and runs a hospital. You'll still lose huge swaths of economic activity, and those people are often the most skilled in their field (certainly the most experienced).
The other thing is that there are plenty of at-risk people under 60. What about people with autoimmune disease? What about the 25,000,000 Americans with asthma? What about the 35,000,000 American smokers? It's not unfair to say that you might have 70,000,000 or more people under-60 who are still at-risk. How do you isolate them?
Without testing, there's no way to solve this. We needed to be testing everyone in the country 2 months ago. We've tested less than 1% of our population. It's been a complete and total failure.