1 out of 5 who get this will find themselves hospitalised, so yeah, not a minor illness.
Mortality rates lag behind infections, it will peak a lot in the coming days.
The issue isn't that it is a potential species killer, it's about the people who will lose their lives, many of which would have lived quite healthily for a while, especially those below 60 with pre-existing health conditions. Even then, death rates for the otherwise healthy are considerably worse than your average flu. Plus, with the amount of hospitalisation, non-covid patients will not be able to access the care they need.
The risk is too, if the virus is let to eat through the population, more strains can appear, some of which may be more deadly. If there is more than one strain, after a few months we may lose immunity, and get right back to square one, where we have another deadly virus, possibly with a 2% death rate ripping through the population. Herd immunity doesn't work with the common cold, some strains of which are a Coronavirus!
There is also a lot we don't know. The disease itself or pneumonia could cause permanent damage to people's lungs, or leave them at risk of future disease such as cancers due to DNA damage, etc. The death rate is still up in the air, and this is highly dependent on the health systems ability to take in new patients.