Running out of ventilators would have minimal impact on the mortality rate. Mechanical ventilation is currently only used as a last resort for <5% of hospitalized patients, and even with ventilators many of those patients don't survive.

https://www.cdc.gov/nchs/covid19/nhcs/intubation-ventilator-...

Beds can be added on a temporary basis. Availability of trained healthcare providers is the more relevant limit.

My point is even if hospitals were closed completely, it still seems unlikely that 20% of people who catch COVID would die from it.