And your plan was to do nothing, somehow identify and isolate everyone who's vulnerable, and then wait for herd immunity to develop.
This is a new virus - how could officials KNOW FOR SURE who the most vulnerable people were? Some pandemics have killed many young and healthy individuals. But there was no way to predict (in the early going, maybe not even now) precisely who the vulnerable segments of the population were. You point to some segments as being statistically insignificant - but you forget that those statistics were not available a few months ago.
The Spanish flu is the classic example of what can happen if you go the herd immunity route - most governments in 2020 just could not take that risk.