This is not flu. It spreads faster than flu, it appears to be fatal at least ten times more so than flu (1 in 100 cases ending in death as opposed to 1 in 1000), and it's also something we have no treatment for at the moment.
It's also worth remembering that while, yes, diseases have existed in the past, they've also been devastating in the past. Humanity never has been and certainly never will be wiped out by a given disease, but that doesn't mean we should ignore the threat. Black Death accounted for maybe a third of all Europeans at the time; before that, the Plague of Justinian probably spelt the end of the Byzantine Empire as a meaningful force; when Smallpox and other European diseases reached the Americas they ripped through the local population.
Coronavirus is unlikely to ever reach the same scale, but if we weren't taking these measures then society will pay the price. As it is, Covid-19 is likely to expose flaws in our approach to healthcare that will need to be addressed in time for any future outbreak.