Sure his power level is good enough for the cube but with the competition for slots it is unwise to waste them on narrower gold cards that offer little more than good value
As an example, I'm avoiding Blood Artist effects." So thanks, but Bastion of Remembrance is right out
Level Limit Area B allows you to put all of your opponents bigger monsters in a weaker position, meaning you can play your own XYZ monsters and get rid of those threats
Black Market Connections Black Market Connections is such a nice way to convert life into resources every turn, and with typal decks you can get a 3/2 changeling creature every turn
Turning combat and damage-based removal into permanent board shrinkage changes how opponents block and how long their creatures stay relevant
Karn, Silver Golem From Urza's Saga Card details Legendary Artifact Creature - Golem Rare Whenever Karn, Silver Golem blocks or becomes blocked, it gets -4/+4 until end of turn