Personally, I have transitioned away from these third party IdPs. I have turned to spinning up my own authentication and authorization stack using an open source ecosystem like "Ory".

With just a single helmfile, I can deploy the entire application stack on my local machine (authN, authZ, smtp server,app db, application). Gives me ease that I don't have to rely on a third party vendor just for testing simple app flows. Transitioning to production is a simple swap of DSNs (database connection strings, real smtp servers, ...). Also, no more burning money when running simple tests or performing load tests with dummy users when using an external/managed IdP.

Still need to experiment with how upgrading will work and migration of user data. But otherwise I am a happy user/developer.