The problem isn't the mortality rate of the virus by itself. This issue is when you combine how infectious it is, the ability to spread while not showing symptoms, and the rate at which it causes breathing issues that require medical intervention. If the spread is completely uncontrolled the spike of infections will overwhelm the healthcare system.
So if the mortality rate is normally 2% but medical intervention is needed in 10% of cases what happens to the people that need medical help when there is no more. Then we have to start making triage decisions about who gets treated and leaving the rest to recover on their own(or likely not). This will cause a huge spike in the mortality rate.
Healthy young people, ok sure you're not going to die from it and it's just a flu. That still doesn't lessen the effect of spreading it too quickly and us losing a portion of our population measured in whole number percentages.
If we wait to try to contain it until the healthcare system is stressed then we waited about a week too long. The next much larger round of patients would already be infected and spreading it, just not showing symptoms yet.
There is no containment possible, the only goal is to slow the spread and smooth out the spike.