[wanderer2323]

ADC (Application Default Credentials) is a specification for finding credentials (1. look here 2. look there etc.) not an alternative for credentials. Using ADC one can e.g. find an SA file.

As a replacement for SA files one can have e.g. user accounts using SA impersonation, external identity providers, or run on GCP VM or GKE and use built-in identities.

(ref: https://cloud.google.com/iam/docs/migrate-from-service-accou...)