How can we be confident that zero infection rate would ever have been achieved? They gave it a good shot, in most places over twice as long as had been original

How can we be confident that zero infection rate would ever have been achieved? They gave it a good shot, in most places over twice as long as had been originally planned. At some point, if you're not seeing transmission rates getting at least close to zero, it seems like you have to conclude the plan's not working.