A couple of points to note, the 20k dead in U.K. so far is highly likely a significant underestimation (could even be double) and we’ve still got some way to go so the flu argument is redundant.
The fit and well and the under 70s carrying on with normal life is all well and good but how does that help route economics and the viability of some airlines. Sure, Stansted-Sofia may be fine but how about Stansted-Alicante? Malaga? Could such routes sustain a huge loss of market, disproportionately high in the months such routes are at their weakest