I didn't mean to imply that it was. But it's not ideal. I believe it's optional in Unreal too, so I'm not sure if AAA games use that feature.
GC is also a very blanket term. There are many different types. From what I understand the Unreal GC gives you a lot more explicit control over how and when it runs.
Having written OpenGL applications in Haskell (not games) I can say that it has no such feature. It's GC is also vastly different as immutable functional languages generate a LOT more garbage than normal applications (measured in GB/s).
GC is not the impediment. GC as it is currently implemented in the majority (if not all) advanced type system functional languages is.