It doesn't have to be someone who plays Magic
Once it resolves, you add one red mana for each card in an opponents hand, that mana sticks around through phases until the end of the turn, and then Inspiring Refrain resuspends itself with another three time counters, letting you cast it again later
There are so many powerful abilities attached to Dragons, along with many having great stats, that Crucible of Fire is the most win more card that can be put into any Dragon deck
I wouldnt say its useless in Constructed play, but I dont really see it being anyones first choice unless youre specifically building around adventure cards
As fragile as Geist is as a 2/2, its easy to give evasion to it via equipment or buff via auras
As for Standard and Limited play, we expect to see it a fair bit, especially in Standard, as it could easily slot into the current Simic Ouroboroid or Mono-Green Landfall decks