We also needed something for chocobos to do, and the saddle mechanic didn't exist yet due to the development timelines of Outlaws of Thunder Junction and Aetherdrift
Two-color decks that dont have access to much ramp and can afford a few colorless mana sources can make good use of a Myriad Landscape, whereas green decks and 5-color commanders have much less need for something like this
Mutate turns two or more creature cards into one permanent, merging their abilities, and usually granting a special benefit when you do so - but the specific wording of the rules generates many edge cases you need to be aware of
To make things easier, start by sorting your collection by rarity to find the expensive uncommon, rare, and mythic rare cards
Add them to your Green decks and overrun the competition.
He could even make a decent Commander, albeit one that limits you to a mono-white deck