It isn't just about mortality, it is about the percentage of people who require hospitalization combined with being highly contagious and the exponential spread that can result.
We should have been doing the shutdowns/distancing sooner and to a greater extent than we are doing now. Shutting everything down slows the exponential spread and that means not having hospitals so overrun that people who need to be hospitalized are told to go home. With that happening, it will kill not only people with this virus but people suffering from injuries and illnesses that hit ERs everyday like car accidents, strokes, heart attacks, etc.
The worst-hit areas of Italy have been dealing with this for a couple of weeks now, having more patients than they can treat and they are turning people away who need treatment. Also a not-insignificant number of doctors are dying from this, putting even more strain on hospitals.
A lot about this virus complicates efforts to keep it from spreading into new areas, a higher R0 than the flu, a lot of asymptomatic cases, incubation periods thought to be as high as 14 days for some people, etc.
This is an example of what we are trying to avoid (trigger warning or whatever they say, I guess - it shows a lot of sick patients but is not nearly as disturbing as some videos coming out of hard-hit areas).
Shutdowns of businesses and increased pressure to stay in is going to only increase as testing catches up to the actual spread. We are looking at several months of this at least.
The mortality rate is much higher than flu, and that is awful enough, but it is also being used a lot to mislead people, either to downplay it or to make it sound like a world-ending plague, but the rate of hospitalization is what we can not handle with massive numbers of infected.
Also nearly 40% of those who have required hospitalization in the USA are 20-54 so the "boomer flu" nonsense is almost as stupid as the racist shit being spread about the virus. It is true that you are more likely to recover than an elderly person but it can still make your life a living hell for a few weeks, nevermind the hospital bills potentially ruining you.