Self-isolation reduces the risk by the largest factor, maybe up to the 99-99.5% level. Guess who cant self-isolate? Doctors.

Wearing a mask, if the entire population is infected, provides a benefit because you are surrounded by infection. Guess which person spends 8 hours a day in a highly infected population? Doctors, especially in the intensive care unit.

If you were worth as much to humanity as a doctor, as an ordinary person, your logic would save fewer lives. However it would increase your chance of being saved.