AWR used to be simple when most databases were single-instance, single-tenant, and all important workload stayed on the primary database.
That world is mostly gone.
Today, one CDB may host multiple PDBs. Reporting may run on Active Data Guard. Read traffic may be pushed toward True Cache. Replication may be handled through GoldenGate or XStream. When performance breaks, the first question is no longer just “what was the top wait event on the database?”