Actually, this is not exactly true. There are actually a lot of people who are infected with the flu who are asymptomatic[1]. Based on my amateur research it

Actually, this is not exactly true. There are actually a lot of people who are infected with the flu who are asymptomatic[1]. Based on my amateur research it does appear that the difference in severity between age groups is more pronounced for COVID-19 than for the flu, though. Part of this may be sampling bias, however, since we are probably catching far more asymptomatic COVID-19 cases than asymptomatic flu cases. [1]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4586318/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4586318/