Can somebody with field expertise explain this to me: The mortality rate is said to be between 3 and 5%. Experts are also saying that it does not draw an accur

Can somebody with field expertise explain this to me: The mortality rate is said to be between 3 and 5%. Experts are also saying that it does not draw an accurate picture of the situation because people aren't being tested nearly as much as should be required. So the question then becomes, why aren't we ramping up tests among the general population to get a better idea of who to prioritise ? Surely if we know who needs urgent treatment and who doesn't we don't have to freeze the whole economy and put everyone in lockdown ? What am I missing ? Am I being too naive ?