The Princess Cruise has nearly perfect data as everyone in a controlled population was tested. (This is not true for South Korea, which has tested less than half a percent of their population.)

The fatality rate was 0.8%. The majority of their passengers were over 60 years old, so even this number is too high compared to the global population.

Yes, the Princess Cruise tells 0.8% might be the best case fatality rate with a functioning medical system.

Even that would be catastrophic for if the virus infects a large percentage of the population, as it is rapidly moving to do. Thus we cannot be even in the least bit sanguine on this and need to move with speed against it. This is in no way comparable to 2009 or other recent events (contrary to your ggp).

As I mentioned, the cruise ship was full of old people, so no, it's not the best case scenario. It's likely the worst case scenario.

No, the worst case scenario is not medical system to help the people who become seriously ill, which 20%, according to WHO and multiple other authorities and statistics.

It doesn't matter if 1% is "optimistic" or not. 20% infection + 1% best-case fatality rate is enough to knock the health care system and begin knocking out the whole of society.

Basically, there's enough information currently to tell people who pay attention and consider rationally that we need to spend every possible effort confining infections and quarantining, basically the entire earth. There is no alternative.

Lots of smokers though