Science has progressed tremendously since the 1918 influenza pandemic. The microorganism that caused it was unknown at the time. That influenza is caused by a virus wasn't discovered until the 1930s, and a vaccine wasn't available until the 1940s. The actual strain of H1N1 that caused the 1918 pandemic was not fully identified until 1997.
The SARS-2 coronavirus that causes COVID-19 was identified and fully sequenced within 2 months of its first known emergence, and vaccine candidates were developed within days of that. Even Anthony Fauci believes that more than one of them will work and be available around the end of the year.
But knowing how the virus affects the human body and spreads can still only be determined by observation, and statistical analysis of those observations. Unfortunately good statistics requires a lot of observations, and even more unfortunately these observations are often in the form of deaths, and especially rare outlier deaths that indicate some of the more unusual ways the virus kills, which take even more time to accumulate.
And until a vaccine is available, the only way to reduce the spread of infection and deaths is through the age old practices of isolation, quarantine, and social distancing. The effectiveness of certain specific measures such as masks, surface disinfection, eating in restaurants etc. can also be measured only after the accumulation of even more data, often much more subtle and difficult to obtain than deaths.
But hey, yeah, let's just throw away our public health infrastructure because their experts haven't been 100 percent correct on a brand new disease and in an instantaneous fashion, or have had to go back and revised recommendations after more data has been collected. Things worked just fine back before science, right?