The problem with airborne infectious diseases is that in order to protect that "minority" that has a high risk of death you have to ensure the spread doesn't us

The problem with airborne infectious diseases is that in order to protect that "minority" that has a high risk of death you have to ensure the spread doesn't use the "majority" that doesn't have the high risk to reach the high risk people. You do that by limiting contact between people, social distancing, wearing masks, etc. The end game here for the high risk individuals is to buy enough time for us to vaccinate a large enough amount of the population so that then there's no need for a lockdown as the virus just can't spread in a largely immune population. But lockdown and the other measures aren't just meant to protect the high risk individuals. We still don't understand how the virus affects many lower risk individuals long term because it's a very new virus. Strictly looking at the "death rate" may make us miss that significantly large portions of recovered individuals (from the lower death risk segment) develop long term health issues that may significantly reduce their lifetime expectation. And yet another reason for lockdown and the other measures is to keep the health system afloat for the other, much higher death risk, health conditions. If our entire ICU capacity is occupied with COVID patients we won't be able to offer the same quality treatment to much higher risk situations like in emergencies (accidents of every kind) not to mention the COVID death rate itself may spike a lot higher if we can't provide the same quality of health care that we've been able to so far.