The experts, by and large, did ok.
For example, cloth masks were a quite reasonable measure against the strains in circulation in April of 2020. R0 was only 2-3 back then. You didn’t need much. You just had to do it consistently.
Unfortunately, we had a national disinformation campaign dedicated to talking people out of wearing the masks. A few thousand epidemiologists and air quality engineers aren‘t going to out-shout Fox News. So we had maybe 50% compliance. People would wear a mask at the grocer, but not when friends arrive for dinner.
That doesn’t mean the original advice was bad. Most advice fails when you don’t follow it.