(Public Health England in the UK had a fairly competent, though not totalitarian-level, contact tracing program. They stopped a while back because it became evident that despite their best efforts, the disease was becoming so widespread that it was reaching the limit of their contact tracing resources and most of the infections were probably unknown community spread that couldn't be found via contact tracing anyway. Other countries are likely similar.)
As it stands, my country is still in relatively early stages compared to many others, and contact tracing became unviable as a first defence well over a week ago. Over 60% of our cases are community transmission.
We're still doing contact tracing, it's probably worthwhile, but it's not going to be a major factor in mitigation.
They just announced it's had 1M installs (in a country of 8.7M) in the last week.
It's largely irrelevant though. As much as it may help a little, this just isn't manageable through contact tracing. While Singapore are being lauded for their CT approach, they've still largely been successful in their efforts due to social distancing (and a culture of widespread adherance), along with things like widespread testing, and effective govt. communication of data.