Beyond the surface-level novelty of seeing such an odd combination of characters facing down Phyrexia together, this is actually an incredibly solid card, and a powerful value engine for any Temur-based (green/blue/red) deck going forward
Rites of Flourishing is a group hug card that helps all players equally, but it creates a problem in other strategies because you spend your mana on a card that helps everybody
The opponent cannot answer the full Admiral board
As mentioned, it's possible that the card will enter circulation properly in later sets and expansions, but for now it's only for those who could beat the event itself
As such, the creative team is always trying to find new choices for the humanoid races of white and blue
they were just shipped out within the space of a week, and retailers could start selling them as soon as the sets were received