Dont get me wrong, the difference between the usually 5 mana and 4 mana for this effect can make a difference, but you can only target things in your own yard
Champions of Kamigawa may have legends all over the place, and plenty of them are not your commanders
Depending on the type, each set will normally have its own theme, either based around a particular fictional setting in the lore, or perhaps tailored to one particular mode of play, like the Commander or Modern formats
The restriction on historic land hurts, but there are some legendary lands and artifact lands to make up for it
In Pokmon Trading Card Game Pocket, opening either the Genetic Apex Mewtwo, Pikachu, or Charizard booster packs freely will likely set you back on your way to building a full collection and a competitive deck as each one offers different cards and different early-game rewards