The effect of Max Balloon is useless against most of the field, but it does wall out the odd deck that only uses Basic attackers such as Regigigas and Blissey/Miltank
Thats not entirely accurate
Flickering creatures has become a more and more powerful strategy as more powerful creatures have been printed
Since Magecraft cares about copied spells, Archmage Emeritus becomes an ally that can refill your hand in a couple of spells
A 2 mana 2/2 creature that can be played in response to a fetchland like Wooded Foothills, a watered down version like Fabled Passage or Terramorphic Expanse, a ramp spell like Three Visits, or another means of cheating cards into play like Kodama of the East Tree in order to ramp out one Plains card from your deck is already good value
4: Until your next turn, whenever one or more creatures attack one of your opponents, those creatures get +2/+2 and gain trample until end of turn