We should have closed China's borders in November
Sure, and I should have invested every cent I have in Google the day it IPOed. It would have required exactly the same ability to foretell the future. The first information that there MIGHT be a problem was on December 29th.
Even the mortality rate for over-80s overlooks the fact that for every "confirmed" case there are probably 50 or more that never come to the attention of the authorities because people are either asymptomatic or follow current UK advice, take an aspirin and stay home. And none of the published rates distinguish between people who had significant comorbidities, and who were going to go as soon as they got cold, flu or just about anything else, and those who were still in good shape, regardless of age. Once you take all that into account, this all looks a lot less panic-worthy.