Care to expand on this so perhaps Postgres people can attempt to make it better?

I've always hated how Postgres merged users, groups, and roles. Users and roles are different in Maria and last I checked, all three are different in Oracle.

I can see how Postgre's evolved that way out of history, when MySQL was thought of as a toy DB. It seems like they added features as a reactionary action then merged them to simplify and now we have three things that are essentially the same. It leads to confusion organization by organization.