If the current rate of death by Covid isn’t enough to warrant precautions, what would that number be?

If it killed one in ten people it infected, would masks and lockdowns be appropriate? If you had only a 50/50 chance of survival, would that do it? If the bug had a 98% death rate? What’s the number? If it killed every person who caught it, should we all just take our chances without distancing or masking? Could any future disease be deadly enough to warrant forced closure of businesses and stay-at-home orders?