I have, and the basic username / bcrypted / scrypted password / JWT implementation was quite easy. What I found difficult* was all the accessory quality of life functionalities, e.g. password reset via mail, automated backups, 2 factor authentication, social login etc. You might not want all of them, but email verification / reset is kinda the expected baseline and it means you have to use an external mail-sending system anyway.

*difficult not as in "hard to implement", more as in "lots of moving parts, hard to maintain"