Besides, we see far more than those numbers die in those age groups every single year from other causes and we don't freak out about it. The Viet Nam statistic is hollow.
More importantly, COVID is an amateur level pandemic. Think about this: The "Spanish" influenza pandemic of 1918–1919 caused well over 50 million deaths worldwide (that would translated to several hundred million today). Moreover, an estimated one third of the world's population (or ≈500 million persons) were infected and had clinically apparent illnesses (1,2) during the 1918–1919 influenza pandemic. The disease was exceptionally severe. Case-fatality rates were >2.5%, compared to <0.1% in other influenza pandemics .
Now... did we shutdown society and crush our economy and destroy our children's futures back then in response to the Spanish flu?
Naw! We let nature take its course and defeated it the same way humanity has always defeated viruses... herd immunity.
Link: https://www.statista.com/statistics/241572/death-rate-by-age-and-sex-in-the-us/