The needs for Auth & Auth are different for public-facing apps/services. It's not entirely unsurprising many newer Auth solutions don't even attempt to implement SAML et al.
With all of the recent steep price hikes in the Auth SaaS space, it seems it's becoming increasingly important to actually own your user account data. By own, I mean have access to the database and be capable of migrating it somewhere else (even at a large inconvenience) if necessary.
KeyCloak seems awesome for this - but I am liking the "explosion" of new Auth providers that seem to be popping up everywhere these days.