we could end so much security pain by having a dedicated display for authentication. It’s not like a second display is very expensive anymore…

That's more or less what you get when enabling MFA with Authenticator on your iPhone.

Banking used to have dedicated dongles with displays before but now also changed to apps. Yubikeys don't seem to be as popular as they deserve. People simply want to carry less things around that can be lost and it's hard to beat the security/convenience ratio of Face ID.