Authn / Authz
Authentication and Authorization
Using OAuth 2.0, specifically OpenID Connect is a good way to handle authentication for your app. Having personal identifiable data and having to protect the privacy of the users' data is a liability which is better left to third parties.
OAuth 2.0 has other capabilities beyond those supported by OpenID Connect.
If developing software for developers and you want specific integrations it is better to use specific capabilities provided by the third party.