Auth0

Is a paid service that handles authentication.
free tier up to 7.5k monthly active users.

offers a platform, admin panel.
embeds, libs,
all types of auth flows and socials integrations: OpenID (social media), Multifactor Authentication (MFA), biometrics,

somewhat ironically, Auth.js (NextAuth) integrates auth0

Unless the project has some specific big enterprise requirement that I can't imagine right now, implementing my own authentication is better practice and free...