Because no part of the ability targets, your opponents cant protect themselves with effective that give them hexproof, like Leyline of Sanctity or Aegis of the Gods
Those who do (likely all of them) look at the top card of their library at the same time, then they decide in turn order where their card goes
But the people united to seize victory from the jaws of the beastmen, earning themselves temporary respite from a life-and-death struggle
While the main focus of this set was obviously cramming in as many important characters as possible, it's not only new cards - there are some choice reprints as well
With the banning of Underworld Breach and the ensuing decline in artifact cards like Grinding Station, Mox Opal, Mox Amber, and Mishra's Bauble, the metagame has shiftedand so has the role of Karn, the Great Creator
Hence, it really only sees play in Commander