Singapore isn't. (the government that is building this app). Neither is Taiwan. Through a combination of contact tracing, surveillance, national health databases and enforcing compliance of quarantined individuals by for example regularly checking in on them they have been able to both contain the spread of the disease and keep a reasonable amount of economic and social life intact.
I will continue to be mystified by this weird and abstract notion of privacy that keeps others away from my data but results in mass lockdown, quarantines, shutdowns and curfews, while people in Singapore give some data to authorities and they can still go out and live their lives. I want material freedom to buy groceries and go to work, not some sort of religious dogmatic privacy while some plague wreaks havoc and I need to haul up in my apartment for months.