In fairness, we know the raw data is crap. But there is enough information to make reasonable estimates of the truth. The raw data says nationwide the mortality rate is about 4%. We know that’s nowhere near true. So no expert makes that claim.
The real number has a huge margin of error, but if people who know wtf they’re doing say the real number of cases is, say, 10x to 20x the positive tests, you can at least calculate a mortality rate of between .2 and .4 and know you’re a lot closer to the real number.
We also have pretty decent data to compute the relative mortality rate between aged groups.
So it’s not like we can’t have some handle on the numbers. You just have to realize a)the raw data doesn’t mean much, and b) our best estimates have a wide margin of error.