There's an old adage: If you think auth is easy to write, you probably don't know auth.
I obviously don't know how much it compares to your specific case, but as general advice it's often good advice when phrased less antagonistically: don't roll it yourself because the rabbit hole is deeper than you expect.
On that front, you may think you are paranoid enough, but keep in mind that the service products sometimes have a multiplier effect in play: N developers of various levels of paranoia, M people in various ops/InfoSec/auditing roles, X committees/layers designed to minimize corporate security risk.
If auth isn't your job and isn't your core competency, many times it is worth asking if following the rabbit down the hole is worth the time you could save outsourcing to a multiplier effect of a team that focuses 100% on those tasks. As with most "buy versus build" discussions, it's not just about "comfort" but leveraging those multiplier effects. Can you pay someone else for the years of experience and "rabbit hole wandering" and multiple layers of security audits? Auth is a "must have" feature for most products but in and of itself is mostly a security liability and mostly pure overhead: no customer is paying you directly for your auth features, auth is the annoying hurdle to features that they do care about and will pay you for. All that time spent on auth and auth security audits rarely appear to provide good returns on investment for your product and your customers. Time spent on auth is time wasted from user-facing features.
I've never head that adage. I did hear one from Miles Davis that says, "If you have to ask, you'll never know." I ask a lot of questions though so I never paid much attention to old adages I guess.
If auth isn't your job and isn't your core competency
I'd argue, it sort of is a core part of any web dev's job and any who neglect diving into it do so at their own risk. Maybe I come from a different time or place than what's the contemporary norm, though I'm okay with that. The main issue I have is with company-sponsored blogs and comments that will just blanket state you should never roll your own auth (because you can pay us instead, oh and btw, we rolled our own auth so you don't have to).
I can understand skepticism with company-sponsored blogs. For what it is worth, I don't have a product to sell here in this space and make no commissions.
As a user, I subscribe to haveibeenpwned alerts on my main email addresses and have been for multiple years. I think there are fewer humbling "[hackers leaking my users table] won't happen to me" reminders than that. It happens to everyone. The ones listed in haveibeenpwned are just the tip of the iceberg and the ones we know about and have been confirmed/verified.
As an enterprise developer, I've been a part of some of the worst security audits imaginable. Thankfully those were all preventative industry requirements, and I'd hate to have to deal with "the real thing". Those audits always come with a reminder: the most secure data is data that you don't have, anything else it doesn't matter how well you think it is encrypted at rest is a liability.
As a user I never want to have to setup another password ever again. I realize that's a pipe dream and we are still at least a few standards away from making that dream a reality, but I believe in it and I've championed it when I've thought standards got close. (I was a fan of the original, now dead OpenID [but not the Zombie OIDC wearing its skin]. I thought Mozilla's Persona/BrowserID was brilliant and killed too early in its infancy. I'm hopeful for Webauthn.)
As a developer I never want to own another database table with passwords stored in it. It's low hanging fruit that every attacker is looking for. I don't care at this point how those passwords are salted, hashed, encrypted, mashed, or other waffle house preparation keywords. Attackers still try to pull the records no matter how safe you think they are. Not having them at all is just entirely easier than worrying about having them.
I don't entirely care how I get rid of the password table. I've paid for solutions. I've used passwordless tools like "magic links". (To use those right you often need all the hard lessons of JWTs and other token types and keeping those secure. It's not necessarily "easier" or "harder", but a lot of knowing how to do it right transfers.)
I just believe pretty strongly at this point that the best password table is one that you don't have and don't have to manage. No matter how easy it seems to "just bcrypt it".
There's a lot of food for thought there and I can actually get on board with a lot of what you said. I enjoyed your perspective at the very least. I too have been a part of some tough audits, fedRAMP, etc. I've worked on apps that regularly get pen-tested. XSS is real, though more often I've seen ITOR issues. No need to worry about being hacked when you're giving it away for free. And then there were at least four OWASP courses I've been asked to do for work.
I'm not quite to the point of never wanting to own another user table with a password column. Maybe I will be someday. Yes, it's a liability but I still think my table (which lives on RDS or Aurora btw) is less of a target than Okta's users tables, which were breached earlier this year. BTW, Auth0 was recently acquired by Okta.
But yeah, if I was spinning up a large-scale, enterprise-level web app, I'd probably tell my stakeholders we were going with AWS Cognito or something, just to offset liability. Never mind, I'm still going to have to have a users table, and if I'm using Cognito for authorization (group-level authorizers) then god help me (check out their limits on those custom fields too). And btw, they use JWT, and their front-end solution Amplify still uses local storage to hold credentials. And it's going to be even more difficult to set up the basic auth flow than if I rolled it myself, but who cares, as soon as the execs hear AWS solution or cloud-native, they nod and feel assured. After all, the liability is now somewhere else as you said. Never mind there's a host of missteps and other ways you could still mess it up on your side of the fence there.
For all of my personal projects, a few smaller paid side-projects, and at least two enterprise-level products, I've rolled my own and owned the DB and it's felt much better to me than the alternatives I've had to face when I forced into some auth as a service solution. I've done auth0 twice (never again). Firebase once. Cognito at least 4 times. I still prefer to roll my own. Maybe I am a masochist. Maybe I've been lucky. Maybe I just go against the grain and do things my own way, providing less of a common attack vector.
The number of devs I've run across who don't even understand the basics of authentication has surprised me. Yes, it's seemingly easy in concept as you say, to "just bcrypt it" but it astounds the number of devs I've come across or worked with who didn't even understand what that was or what it looked like. Then we have the "company-sponsored blogs" and the echo chamber of people throwing down absolutes of "whatever you do, never roll your own", "you don't understand how hard Auth is", etc...
But I'm coming to accept that maybe I'm in the minority on this topic so I'll stop ranting for now. I suspect that a lot of us on this thread are speculating or speaking from different scenarios and experiences, like a sysadmin or IT head, vs legacy enterprise apps, vs mobile, front-end specific SPA's with stateless auth, vs server-rendered stateful, session-based web apps, etc...
In any case I appreciate you taking the time to map out your thoughts and perspective in detail and I think it's probably broadened my own thoughts on the subject.
I obviously don't know how much it compares to your specific case, but as general advice it's often good advice when phrased less antagonistically: don't roll it yourself because the rabbit hole is deeper than you expect.
On that front, you may think you are paranoid enough, but keep in mind that the service products sometimes have a multiplier effect in play: N developers of various levels of paranoia, M people in various ops/InfoSec/auditing roles, X committees/layers designed to minimize corporate security risk.
If auth isn't your job and isn't your core competency, many times it is worth asking if following the rabbit down the hole is worth the time you could save outsourcing to a multiplier effect of a team that focuses 100% on those tasks. As with most "buy versus build" discussions, it's not just about "comfort" but leveraging those multiplier effects. Can you pay someone else for the years of experience and "rabbit hole wandering" and multiple layers of security audits? Auth is a "must have" feature for most products but in and of itself is mostly a security liability and mostly pure overhead: no customer is paying you directly for your auth features, auth is the annoying hurdle to features that they do care about and will pay you for. All that time spent on auth and auth security audits rarely appear to provide good returns on investment for your product and your customers. Time spent on auth is time wasted from user-facing features.