First, testing is unquestionably becoming more available, so as the number of confirmed cases increases, that number is greatly influenced by increased testing, not just more people contracting the virus. As health experts will tell us, testing for a virus like this is a very good thing when it comes to slowing the spread of the virus. The more people tested, the more people who are infected will be identified, and more lives will be saved as a result.
Second, the low number of confirmed cases we see now is actually the result of the inverse of the surviorship bias (or fallacy) where instead of "dead men don't tell tales," we have "mildly infected men (people) don't tell tales." Due to mild cases that are indistinguishable from the common cold—and even those cases that present no symptoms—the number of people infected is almost certainly far greater than reported. However, virtually everyone who dies from the disease will be tested and counted, at least in the United States and likely other developed countries. This means that the fatality rate, as well as the percentage of "serious" cases, is actually likely much less than reported figures.
To "spell out" the math here, we calculate the fatality rate by dividing the known number of deaths from the virus (numerator) by the known number of people who have the virus (denominator). If we don't increase the numerator (the number of fatalities) but do increase the denominator (the known cases), the fatality rate decreases. This isn't some wild theory. Health experts agree that several factors, including the ones I mentioned, lead to a fatality rate that is likely inflated.
To be clear, when the World Health Organization (WHO) and similar authorities post numbers, they virtually always do so with disclaimers and explain what the number actually represents. The problem isn't with the WHO; the problem is with how the public ignores the disclaimers and misunderstands what the numbers actually represent. A fatality rate of .6% is still about six times worse than the flu, but it is no reason to hide in an underground bunker filled with toilet paper (but do stay at home when possible with a reasonable supply of toilet paper).