It's just another layer on top of an already well built crypto system.
It can prevent someone that gains physical access to your yubikey from easily using the device.
It might not stop a very advanced attacker, but it at least makes things more difficult.
No. Passwords can be phished. Even password+OTP has proven to be weak. This cannot be phished, and it’s far more user-friendly.
The fingerprint is not a password replacement. The yubikey is a password replacement. The fingerprint prevents a random person from using your yubikey before you notice that it’s gone and you revoke it.
It can prevent someone that gains physical access to your yubikey from easily using the device. It might not stop a very advanced attacker, but it at least makes things more difficult.