Right -- which is why that isn't a sufficient condition for restoring normal life, where people can go to weddings, concerts, festivals, church services, sporting events, and other large gatherings. To get back to that, we need the virus to be gone, or we need herd immunity. The only way we are going to get there fast is if we fail badly and let tons of people die unnecessarily. The goal is to do it slowly so we can take care of sick people properly.
I don't agree that we can get herd immunity without mass death. First, the fatality rate is still high even with medical care. Second, it would take years to process everyone that needs to get it through proper medical care.
Finally, to do the flatten the curve strategy, you need to get R0 at exactly 1.0. Too high and it blows up again. But if you get it a little too low, and you keep it there for a while, the virus just dies out. If we're capable of keeping R0 at exactly 1.0 for five years, we're certainly capable of keeping it at 0.95 for two years until we have a vaccine.
Consider that it takes days-to-weeks for patient-zero to show symptoms, another couple weeks for symptoms to appear in spreadees, and still more days for the government to responds with strict enforcement. This kind of feedback loop will make this kind of control impossible.
South Korea and Taiwan show that this kind of control is possible.
It is pretty amazing to watch how quick we are at giving the benevolent government a dystopian level of control.
Once the case count is sufficiently low, we just need R0 to be less than 1. 0.9 is sufficient. That means that each case infects 0.9 people on average. To do that, we're going to need everyone to wear masks, stop having big gatherings, aggressive rapid testing, and electronic and human contact tracing.
The low case count we're going for with the lockdown does two things. First, it stops mass death and hospital overload. Second, with fewer cases, you can actually allocate the manpower to trace all of them thoroughly.