Next, explain why the inventor of PCR said it shouldn’t be used for diagnosis at all.
Really? Kary Mullis, who died in August of 2019 and could not have possibly have known of SARS-CoV-2, said that?
Since his invention of PCR, the technique has been adapted for dozens of uses. To my knowledge, Dr. Mullis never once stated that he thinks PCR is not suitable for diagnostic purposes. If you have a reference where he said that, I'll gladly take a look and see exactly what he said.