I agree you shouldn't write every line by hand, you should use libraries, but pretending like OAuth/ODIC require using something like Cognito/Auto0 is just silly. An LLM can crank out the needed code in very little time and give you full control over your auth instead of fighting an auth provider at every turn.
The number of compromises something like Cognito requires are just not worth the perceived gains.
I really whole heartedly disagree and if you think it’s silly I think that you don’t really fully understand the complexity of it. An LLM doesn’t solve everything. You still need to understand the spec, become a domain expert, and design your solution for the parts that the RFCs leave open with undefined behaviour. At the very least if this is your opinion you should start with an open source solution like Keycloak or authentic and fork it if you really need “control”.