You can read about the medical research coming out about Covid-19 by using google scholar. Some potential reasons for the level of panic:
1 - Somewhere around 20% of known cases progress to "severe" illness requiring hospitalization. A major concern is that if enough individuals become severely ill within a short period of time, hospitals will be totally overwhelmed.
2 - Some of the cases where individuals have recovered necessitated external oxygenation for several days (imagine an ongoing blood transfusion type process in which a machine oxygenates the blood and pumps it back in because the patient's lungs are shut down).
3 - The amount of viral load appears to matter, as a disproportionate % of hospital staff have become severely ill and died despite being otherwise young and healthy.
4 - This disease's fatality rate appears to be approximately 40x higher than the seasonal flu, with similar rates of infectiousness. Unlike the flu, humans frequently do not develop immunity to coronaviruses post-infection (there are something like 4 viruses that cause a cold, but you get more than 4 colds in your life).
5 - Many individuals who have recovered have suffered organ damage (lung, heart, kidney), and may be more likely to die upon re-infection.
6 - The ability to care for the sick becomes extremely challenging as hospital workers are infected, and those who are not infected are deeply demoralized by caring for their colleagues and watching them die.
It's not my intention to freak anybody out, but complacency is frequently a major (and preventable) risk factor in an emergent infectious disease outbreak such as this. It is likely that daily life will look very different for a lot of people for the foreseeable future, and it behooves us to mentally prepare for that.
Personally, I am losing sleep over this situation as someone who works with individuals who are incarcerated and severely mentally ill. Once this thing gets into jails/prisons/psychiatric hospitals, it could easily become a severe crisis.