I found Keychain quite horrible. Everything is or at least felt just too abstracted away so that I don't feel in control of my secrets. Might have been just the UI though. And then it's obviously not crossplatform by default. Sync your password database between your Android phone and Mac? Nope. So it's another step into vendor lock in.
Keychain supports some pretty great stuff like WebAuthN and 2FA codes. It’s UI is kinda bad though. I’m all-Apple and techy, so it works great for me.
The Keychain integrations and UI have improved a lot over the past couple years. That said, I still use 1p for family sharing.
As a regular user of Android, Windows, and Linux systems Keychain is almost worthless.
I agree it’s so easy, if they add some sort of plugin that pushes to you phone to verify It’s you - game over.