Hey there!
I understand the frustration. However macOS requires at least one administrator password to control a Mac. It used to be you could use a blank password, but believe that’s no longer the case.
Most if the time, if I talk with someone who says they’ve never had a Mac password set, it’s usually not because of that, but because they’ve become accustomed to the automatic login features, as well as other options, such as unlocking with Apple Watch.
FileVault encryption I believe requires an admin password every time you log in:
How to log in automatically to a Mac user account - Apple Support
Change Lock Screen settings on Mac - Apple Support
https://support.apple.com/102633
These articles should help!
I have however seen times when a correct password does not work, although rarely.
Usually when this is the case, there is a keyboard issue, where as it defaults to the wrong keyboard input, or there is a stuck key, or there is a nearby Bluetooth keyboard that has a key being held down by something.
Otherwise, there could be an issue with the firmware that requires the firmware to be restored, any Apple Store can do this, or you can yourself if you have the right equipment:
How to revive or restore Mac firmware - Apple Support
Anyhow, hope something here helps out, to you or anyone else!