You can live to an old age with common conditions like diabetes, vitamin D deficiency, and subclinical heart issues.
Also, unless you think old age is a curable health issue, shutdowns are still the only way to keep people in that group safe.
> improving diets and removing pollution from the air
How does one improve the diets of billions of people in a few days?
Shutdowns are instant. Major overhauls of civilization are not.
https://www.wfla.com/community/health/coronavirus/new-cdc-re...
Did you know almost nobody died of HIV? The vast, vast bulk of AIDS deaths were due to systemic collapse resulting from unchecked infections that set in when the victim's immune system was destroyed by HIV.
Given that information, would you be okay refraining from treating an HIV infection if you had one? Do you think the time and effort spent stemming the AIDS epidemic was wasted?
In fact, without being a scientist, AFAIK this is one of the major problems of science and how it is consumed, understood, and used/abused in society at large, but also within the publication realm itself. If a certain scientific finding is boring and merely confirms something else (which is critical in science), there are less incentives to do it. As a result, truth becomes characterised by 'sensational' things, not necessarily true or accurate things. Scientists and followers of science fail so much to see our own biases and shortcomings. We're getting there, but we're hampered very much by our human nature.