Metal-type cards can resist attacks a little easier than other types of cards
A 3/4 flier for four mana that mills 3 cards on attack feels more like a draft card than the face of a Commander product, even if you do get to keep an artifact creature or vehicle from among those cards
Look for certain telltale signs such as: Poor card quality
Then, anytime you cast another colorless spell with Ugin in play, you'll exile another permanent that is one or more colors
Still, this kind of library manipulation at this low of an opportunity cost is just too much, so I would not be surprised at all to eventually see it banned in Modern, as it already is in Pioneer and Standard
Brenard, Ginger Sculptor Im here for the golem lord, but Ill take the Food lord while Im at it