I have seldom come across unix multiuser environments getting used anymore for servers. Its generally just one user on one physical machine now a days. I understand run0's promise is still useful but i would really like to see the whole unix permission system simplified for just one user who has sudo access.
We use Userify which manages multiple user logins (via SSH) and sudo usage.. there are definitely many, many use cases for teams logging into remote servers, and most security frameworks (PCI-DSS, HIPAA, NIST, ISO 27000) require separate credentials for separate humans. Sudo has some issues, but it works very well and is well understood by many different tools.
It could all be simplified and map one to one to your identity provider credentials at a higher level. Having a complicated user system on the servers makes it a problem.
Userify doesn't seem complicated.. it is just Linux users, created with adduser just like you'd type in at the command line:
https://github.com/userify/shim/blob/master/shim.py#L227