Those complexity rules are the result of an entire industry blindly following the best practices of an old unix DES crypt function. It's dumb and it should stop.
If I wanted a single number, say, '1' as my password, why shouldn't I be able to use it? It is my account and my responsibility, why does everyone feel the need to enforce something on others.
A simple warning would suffice.
In a scenario like GitHub's organization (where one user has privileges over many shared resources), for example, its owner still carries the responsibility of safety of all its resources.
If it's possible to escalate privileges, then that's the place that needs fixing.