Masks did nothing?
The number of flu cases in the U.S. fluctuates by year. Over the past decade the yearly number of cases ranged from 9 to 41 million.
www.statista.com
The number of flu deaths in the United States fluctuates by year. Over the past decade annual deaths ranged from around 5,000 to 51,000.
www.statista.com
And, if they were only 20% effective, that is the percentage of of infections prevented by COVID.
MAny Asian countries have been wearing masks in public for years now. They were common among Asians in the Bay Area in the 1990's, long before COVID. In high population density areas they are probably still a good idea.