Well assuming everyone has it is a faulty assumption as there is just a small percent of the population that has it or has survived it.
I have no problem with everyone wearing a mask but the only way we get a handle on this is testing. Testing for people who already had it and for people who have or have not had it. This should not be difficult to understand if we want to eliminate this virus. It's the strategy followed in past pandemics. In the absence of a vaccine and treatment then only social distancing and testing and strong contact tracing will isolate the virus to get some modicum of control.