Its ability to fetch key lands like Mutavault or Phyrexian Tower makes it an essential piece for the deck
you can't cast it without discarding a card, and you can't discard additional cards
You can also strategically time your Alteration to stack the abilities of two different creatures
Each of those permanents attacks its owner if able, not necessarily the player you gained control of it from
Nowadays, we take for granted the implications of eight one-drop accelerators on mana curves, green decks featuring flexibility instead of just being Stompy beatdown decks, and the use of Natural Order to let a stupid green deck function like a combo deck
Jumbo Cactuar will be Standard-legal, by the way that is to say, it'll be printed in the main Final Fantasy MTG set, rather than the Commander precons revealed on Monday