A way to recognize that the downside is minimal is that if Ugins Conjurant is ever on the battlefield with fewer counters than it started with, Ugins Conjurant traded for more than one card and is hence card advantage
It was indeed made to counter one of the strongest cards in the game, and thats why it is almost always a fixture in dragon-themed decks
Yavimaya, Cradle of Growth also gets used in EDH for the forestwalk enabling, but thats pretty niche
About Kefka, Court Mage // Kefka, Ruler of Ruin Kefka, Court Mage // Kefka, Ruler of Ruin is a card in the Magic: The Gathering catalog on collecto.rs
If you're drafting, then you'll want Draft Boosters
Cards like Luxray GL LV.X quickly dominated competitive play