One thing that IMO makes this a very significant event is the percentage of cases that end up severe. From the Worldometers site:
180 new cases and 5 new deaths in Italy. Among the 472 active cases from an earlier report, 159 (34%) are hospitalized and 37 (8%) are in intensive care.
I've seen reports that about 5% of cases require intensive hospital care. Now, that number might be overstated due to mild cases being undercounted or undetected, but even something like 2% would be a far higher percentage of severe cases than influenza. For example, there are only about 800,000 staffed hospital beds in the US. Let's say 2% of those infected with COVID-19 would require hospitalization. At a 2% rate of hospitalization, 40 million infected persons would completely fill those hospital beds, and that's only about 12% of the US population. A widespread pandemic-style spread could easily infect more people than that.
Another thing to remember is that there appears to be no prior immunity to COVID-19. Influenza kills tens of thousands of people each year even though a whole lot of people get flu shots. There is no vaccine for COVID-19, and no one has ever had it before, so no one carries any immunity. Theoretically, every single person on the planet might get infected. That's not going to happen, but if even 10% of the global population gets infected, we're looking at the potential of millions of global deaths.