The assumption you're making is that they have mature offerings because they are big names. Facebook, Google, Amazon and Microsoft have excellent full-featured offerings in every sector they've ever dabbled in? They've never made a bad or neglected product?

This is exactly the problem, the assumption that huge conglomerate juggernauts hoovering up or invading every sector is adequate or healthy competition.

Also that list seems to be very iffy at listing actual competitors to the Auth0 product offering. Much of it looks like services that use OAuth integration for access to their proprietary platform, not necessarily a dev-focused blank canvas for SSO/CIAM integration within your own app. Many specificly list OIDC as No. The list doesn't even have Auth0 on it.