Color complexity Magics five colors (white, blue, black, red, and green) have always been roughly balanced in terms of how many cards each gets
While Karn isn't breaking anything and shouldn't be banned, if we ever get to the point where Karn, the Great Creator finds itself on the banned list (which is unlikely but not impossible), then Mycosynth Lattice would be 100% safe to unban
You can search for it with cards like Crop Rotation or Nylea's Intervention
While 1/1s will take some time to whittle down life totals, cards like Favorable Winds and Sprite Noble can add significant power to your board for very little mana, turning a bunch of unassuming creatures into a dominant board
And no, dont say the groundcrafty reader
Needless to say, this deck can quickly get out of hand