Their arguments are pitiful…
No, it is not.
It does not say that scripture will equip us for every good work. It says that “All Scripture is inspired by God and profitable for teaching, for reproof, for correction, for training in righteousness; so that the man of God may be adequate, equipped for every good work.”
This is a personal interpretation not drawn from the actual wording of the text, but instead from the personal agenda of the writer. The passage does not state that scripture is able to fully furnish one, rather, it states that “scripture is… profitable for teaching… so that the man of God may be… equipped for every good work.”
Meat is profitable for nutrition planning, so that man may be nourished for every physical activity. Does that mean a linebacker can fully perform his duty on a diet of nothing but meat? No! He needs fruit and potatoes to have a well-rounded diet and proper health.
Notice how the proponents of Sola Scriptura are nearly the worst at twisting Scripture to their own agenda?