Because the mortality rate for seasonal flu is 0.1%, and COVID-19 as of right now is 5% (though probably lower once all the asymptomatic people are identified and included in the stats). Because the flu presents symptoms faster than COVID-19, so it's identified and treated faster, slowing the rate of infection. Because there's a vaccine available for the flu. Because the hospitalization rate for flu is lower than COVID-19.
Smart science people say that we'd need 70% of the population to get infected with this corona virus to reach herd immunity - where enough people have had it and are immune to it - to stop the virus from spreading within the general populace. There are ~329 million people in the US, so we'd need 230 million to get COVID-19 to get there. If the mortality rate holds to 5%, that means 11,500,000 deaths. Even if we were able to keep COVID infections to 35.5 million (estimated illness caused by flu in 2019), and using the current 5% mortality rate, we'd lose 1,775,000 people in the US. Both of those are a LOT higher than 34,000 flu deaths in the US estimated in 2019.
Still think this isn't as bad as the flu?