South Korea did contact tracing with success. However, they are a smaller country. If you look at their numbers, their daily deaths since April 17 have been less than 2 per day. That’s down from 8 daily deaths on March 27th:
https://www.worldometers.info/coronavirus/country/south-korea/
From what I read Korea started contact tracing very early when it made sense.
For us to do it now, very little to do with the Whu flu. It’s an excuse.