Looks like it's time for Apple to release Facetime for Android; in the meantime, as noted in the final paragraph of the article, Duo is more likely to be a competitive threat to Skype and Facebook Messenger. Also see Google Debuts New Chat App to Rival Skype, FaceTime (Bloomberg) and Google launches Duo video-calling app, a dull cross-OS FaceTime rival (TechCrunch).
"“You shouldn’t have to worry about whether your call will connect, or if your friend is using the same type of device as you are,” Google said in a statement, in a veiled jab at Apple. “It’s no wonder that nearly half of U.S. adults never make video calls on mobile.”Google Duo Makes Video Calling Between Operating Systems Easier - The New York Times
All of this feeds into Google’s strategy to attract iPhone users over to Android. Google’s apps generally work better on Android devices than on iPhones, so the more that people get hooked on Google’s core apps, the less incentive there is to stay loyal to Apple."