The mortality rate is about 0.6% for people under the age of 70 using CONFIRMED cases. Given asymptomatic rates have been estimated to be as high as 50%, that means the true mortality rate for all people under the age of 70 is probably more like 0.4%. Given the number of people who have already had it and the fact that herd immunity will start to set in, the death toll in the US would likely be something like 300,000, or 0.1% of the population. Still a lot of people, but is the whole country worth destroying for 0.1% of the population?
As for people over the age of 70, a strong effort could be made to protect them. If we went completely back to normal, measures would probably only need to be taken for 2 months or so before we achieved herd immunity, and they could go back to their normal lives.
The case or infection fatality rates are not static. They have decreased as we have learned more and people's behavior have changed. Things that are decreasing the fatality rates include improved treatment protocols, not having overrun hospitals, and higher-risk people doing a better job of hiding. If you go with the OP's idea of pretending it doesn't exist, those higher-risk people, including the old will get infected and up that fatality rate up substantially.
Good evidence for higher-risk people already hiding is the shortage of poll workers (demographic is older people) for upcoming elections. The number willing to work polls is down 90% where I live, at least before the campaign to recruit young people.
The "still a lot of people" dying isn't something that you should shrug off. Why is it OK to shrug off the deaths of 150,000+ Americans so far and be willing to let that continue? Other countries are doing way better. When they do way better, they can do a better job getting their economies going. How good can an economy be when a large portion of Americans need to hide (remember 40% of Americans are obese). China has in person crowds now at CBA games watching Jeremy Lin and company. My 81 year old dad is in Taiwan, and is free to do whatever in crowds because it is safe there. He can't safely come home to the US. Meanwhile my mom is hiding in CA.
A strong effort isn't being made to protect 70+ people. People are still being infected in care homes. Care is provided mostly by lowly paid, generally young workers - people who might be still be hanging around with their peers. Where is support from the federal government to provide strict policies for how to operate care homes during this pandemic and provide things like quick testing before every entry into a care home? Or maybe have support people live in the care home bubble for week or two at a time after they are truly cleared virus free, instead of having a chance to bring the virus in every day?