In my mind the biggest issue with MTG (other than cost) is its mana system. Anyone who has played MTG can tell you about the many times they’ve lost games because they either drew too much, or not enough mana. This problem is so old and common it has a name known by both its players and developers as Mana Screw. While this problem can be managed to a certain extend by good deckbuilding and mulligan practices, there is nothing preventing it from rearing its ugly head in any given game of magic.
Cantrip 