My point is that, what GCs do at runtime (discover garbage) can be done statically in all of these cases. The sole reasons GCs do that work at runtime is because of cycles.

Cycles aren't common at all and the answer shouldn't be "let's create a huge complex GC that handles all cases, then down the road we'll optimize for the common case" the answer should be "let's do the sane reasonable thing that handles the common case and push the problem of cycle-management to the programmer"