It's definitely not a unicorn situation.

Copy and paste is not a skill that requires much technical literacy. I've not seen a Password Manager that makes the copy button hidden or hard to find or need much technical skill to use.

Many "legitimate" websites, especially corporate "SSO", accidentally train users that autofill just doesn't work some of the time. Example Corporation's SSO configuration generally has users put their password into auth.example.com, except when the app in question is using some weird SAML flow and accidentally ends up at saml.example.com or auth.okta.com. An old legacy internal app still needs the password inputted in an HTML Basic Auth prompt due to a redirect through oldauth.example.com. The user learns to just copy and paste and have no idea why autofill works on some internal apps and not others because they have no idea what SAML is or why a legacy app is special/different from modern ones.

It happens on the public web, too, to a lesser extent. A website goes through a "rearranging deck chairs phase" and can't decide if id.example.com is cooler than auth.example.com or if they should just put login only on top level example.com and flip back and forth over a few weeks as different internal teams "win" or various A/B tests run.