It depends on what context you're operating in. The reality is that most people don't fully understand authentication / authorization properly so they often mess up. When you have a small team of engineers that are spread very thin, it might be better to delegate this responsibility. If you have the time and resources to study the topic in depth and implement it properly then it's fine. It's just not that interesting of an area since the space for innovation and creativity is limited, and since the major problems have already been reliably solved by others at best you end up with an equivalent outcome and at worst you end up with security issues.
If you're operating within an enterprise context, Keycloak [0] is pretty massive but provides comprehensive coverage for all authN and authZ needs, and it's open source.
Back when I first started studying this topic I found that reading through a lot of NIST guidelines was helpful. I'd recommend at least browsing through SP 800-63-3 [1], SP 800-63A, SP 800-63B, SP 800-63C to get a good idea of the domain. Admittedly, this might be a lot of overkill for your application and needs.
[1] https://csrc.nist.gov/publications/detail/sp/800-63/3/final