Curious which services under GCP have been shut down? I get that Google killed Reader and that GCP users used Google Domains, but for the time-being GCP has felt safe.
Cloud IoT comes to mind, and the linked thread claims cloud domains is on the chopping block. However, most Google cloud services have a Ship of Theseus thing going on, where they'll deprecate most features of a particular service without deprecating the service name as a whole. Nothing that was written stayed working without constant maintenance, no matter how trivial or important the features (e.g. spending limits in AppEngine).
Google Domains, Stadia, Firestore, Chatbase, IOT Core, Zync render, Cloud print, Jump, Cloud Messaging, Prediction API, Cloud Connect, and the video rendering service. But more importantly, Google has a reputation for shutting things down in general:
