The variance argument may be solid in general but I will say that mana flood and mana screw can be greatly alleviated through deck building and use of mulligan.

The variance argument may be solid in general but I will say that mana flood and mana screw can be greatly alleviated through deck building and use of mulligan. You don't often see it happen during high level play. I used to be rather careless in how I planned the mana of my decks and rarely took a mulligan. I faced mana issues all the time. After putting more planning into my mana base and deciding on a careful strategy for when to take a mulligan I now rarely experience those issues. When I do it is mainly because I break my own rules out of greed when refusing to admit a hand with great cards is too low on mana.