There are lots of 0-mana artifacts in the game, like Moxen and Lotus Petal, even Memnite and Ornithopter
Chocobos, landfall, equipment all work toward a great experience, and the biggest trait going against this introduction of Universes Beyond to Standard is the high cost and demand for the cards
Also remember that some powerful cards were printed as rares because the mythic rarity didnt exist at the time, like Ancestral Recall, Timetwister, and Time Walk
The extra mana, and Avatar Roku are an exquisite filling and layer to this wonderful saga of a card that ends in real firepower
You can have up to four of any card, such as creatures and spells, in your deck
Here's hoping Wizards continues to print efficient, generic answers la Fatal Push that help Modern internally regulate its strongest cards, and that the format remains extremely diverse