Exposure Notifications was a great try by Google and Apple. If it weren't a thing, most big government would develop more privacy invasive contact tracing app. It seems that it wasn't worked well, but still a great try.
Of course we also had another app called Luca, which tried to do a lot more direct contact tracing and turned out to be extremely insecure and leak user data, so there's that. And of course there were some plausible corruption allegations relating to its public funding.
Exposure Notifications is not an app, but a framework and a protocol, and CWA was an implementation of it, hooking in the features developed by Apple and Google for iOs and Android
[0]: https://github.com/corona-warn-app/cwa-documentation/blob/ma...