Gameplay-wise, its not particularly good, as it demands that you constantly feed it Energy for almost overkill levels of damage, not to mention that I personally preferred Arcanine
You are overpaying by a ton for that extra card when you use Think Twice
Like most Magic: The Gathering cards, the value of Decanter of Endless Water depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Commander Legends: Battle for Baldur's Gate)
Carmine is also a really nice supporter to have as you can play it in the first turn which means you can dig for cards much quicker
If you want to see more, look no further than the latest set Duskmourn
Plus, the artwork is quite glorious, featuring a bold Pidgeot in flight against a mystical cosmic background