Looking at the base of each deck: Lands
Fires of Yavimaya decks were as fast as other beatdown decks while packing more power and the ability to get brutal draws, allowing them to be the most important deck in Standard for as long as they retained their key components
It just does too little for the opportunity cost of running it in your deck
View all Archazias Island Enchanted cards below Click to enlarge, double-click to zoom The game-changing Donald Duck Flustered Sorcerer had to get an Enchanted version, and the big bad of the next set (Reign of Jafar) Jafar Newly Crowned Enchanted has a brilliant cross-over art Show me More
Leaning in would mean playing some fun cards that have no other home, like Confusion in the Ranks, Forgeborn Oreads, and various other blue enchantments you like
While Four-Color Keruga is definitely delivering results in the post-ban MTG Modern meta, its a bit too early to call it a problem