You’re missing the point entirely. The flu deaths are in a population that are largely protected by either prior exposure to (one of the many subtypes of) flu viruses or have had a flu shot (epidemiologists predict which subtypes will be present).
This subtype of Coronavirus is novel and has different surface antigens to other circulating coronaviruses. Exposed people will largely make immune cells against the novel surface antigens (also known as epitopes) but it takes time. In that time, vulnerable people may die. We don’t know a few important things about this virus.
Namely:
How long it can survive in droplets or on inanimate objects.
What the average length of incubation is.
Which stages of disease that those infected are infective. Stages include incubation period, disease state, recovery etc.
Until we know more about these questions then the best bet is to isolate everyone.