That means with haste you could cast Ureni, swing for 7 flying, and draw + put two more dragons on the battlefield
And before this tier list I didnt even knew about the Japanese grading company ARS
No need to track 21 commander damage, just one clean hit and an opponent is out
Commander has a ton of powerful ways to generate a bunch of mana, and turning that mana into cards, life, and a Jellyfish Hydra Beast that flies and tramples is pretty much everything you want to be doing in the format
Taking a random one-drop wont stop them from casting two more, and they have enough game-winners that discarding those is rough even when the spent mana doesnt just mean you lose to 1/1 beatdown
Beyond just dragon decks, this card can do a whole lot of work