It's as useful as your gesture knowledge. Even if you know anatomy, your ability to use the thing well relies on how well you can make an interesting form. Otherwise you're better off referencing photos or an artist who can actually make good figures, because you can still astronomically fuck up a mannequin. Pic related.
3D software won't protect your poses from looking fundamentally broken (again pic related) or stiff if you don't have the eye for it. It's never a replacement for reference, and is something you use only when you ***know what you're doing*** to streamline the process.