The restricted page password field is still there and we’re not aware of any issues with its use. You’ll have to share some more information about what you’re seeing, and what you expected to happen as I don’t fully understand what you’re reporting.
Note that a restricted page’s password field does not accept account passwords.
Regarding download keys granting access to a game, an itchio account must be used if the user wants to “claim” access to the page in order to access it.