I'm not sure the JWT characterization is fair, but in a world of open-source, auth doesn't feel like something you should have to pay a subscription for.

Auth0 does a lot more than just a JWT. Sure, it's more expensive and probably not something you'll need, and if you do; why? But it's definitely not just a JWT.

like what?

SSO (for starters)

I use auth0.

For starters I would have no idea where to begin without the SaaS.

Next, it handles account management, signup, password resets etc. You'd have to write that yourself.

is that your take on Auth0 specifically, or SaaS authentication in general?