You know if Polio, Smallpox, and Whooping cough were coronaviruses you might have a point. But ... they ain’t, and you don’t.
I just learned why the COVID virus may be more difficult to kill off than Polio, Smallpox and Whooping Cough. COVID is able to exist in animal reservoirs. That means, even if humans have rid themselves of the virus, animals will continue to carry it. Once a mutant evolves from the animal population that can overcome the human immunity, the virus will reproduce in the human population.