It's actually generic "authentication for the web" which is why it comes off as generic. They started off with being authentication for NextJS and it was definitely helpful for a quick auth implementation. Now it's being opened up to any web framework which is kind of a cool evolution.

It's some JS lib abstracting over some authentication providers. But this doesn't sound sexy anymore.

It sounds like it's similar to Passport.js, which let's you add support for 3rd-party auth systems by just supplying API credentials instead of implementing an OAuth etc flow yourself.

It still leaves a lot of authn/authz work up to you, but it simplifies putting a "log in with Google" button on your site.