[sanderjd]

I don't think you answered the question you're responding to. You're still talking about the app, the question is about all contact tracing generally. Actual epidemiologists appear to disagree with your (I'm assuming) amateur opinion that contact tracing, in general, is useless. They are aware of all the things you mention, and still believe it is useful. There also seems to be examples of success with contact tracing in conjunction with good testing regimes in countries that are faring much better than the US. It seems like arrogance to me to think that we can't learn anything from those successes.

(But I'm very uneasy about these app-based approaches, and much more in favor of hiring tons of humans to do contact tracing instead, or at least as the primary mechanism.)