And tbh I don't think I ever saw a circular dependency in a system
I'm not saying they don't exist of course (or that GC/RC shouldn't cater for them) but it's a very specific use case
A doubly linked list already creates a circular dependency.
True (especially if it's a circular one) but those can be weakrefs/softrefs
There do exist algorithms for resolving them, and that process can too be deferred, but also restricted to subgraphs and only when cycles are possible.