Personally, I really enjoy playing this in Commander purely for the political potential of revealing what cards are in a players hand
If it is face-up, negate it's effects and banish it
Sure, 5 mana isnt an amazing rate for a board wipe, but it is definitely still acceptable for most Commander decks outside of cEDH
Even so, Gong's defense managed to withstand all of the attacks of "Rune-Eyes" and allowed him to set himself up for a win on the next turn
It isnt a brainless damage machine, you have to plan around when to drop it and when to hit with it, but thats part of what makes pulling and playing it so satisfying
This is because Knightmare Phoenix can destroy a Spell or Trap without having to be drawn directly from the deck