In a deck with a five-color commander, it essentially reads, "You win the game if you control your commander." That is not the most satisfying end to a game, and it does begin to become an auto-include for many decks
"Hiro Hamada, Robotics Prodigy", for example, can take an item from the deck and then place it on the top, allowing players to grab it immediately after
Academy Manufactor greatly increases your artifact output
For those, big Shift characters like Robin Hood Champion of Sherwood, Beast Tragic Hero, and Tinker Bell Giant Fairy are excellent (but expensive) potential singers
Force of Virtue and Sunscour use white cards in your hand and are mana-less ways to have a massive impact on the game
Even with this in mind, a few cards have still managed to blow MTG players away