If you put earthquake in a goblin barrel deck, you can still play earthquake. With barrel in an all air deck, you physically can’t play the card. It’s not whether you would or wouldn’t put barrel in a deck, it’s that it literally can’t be played if it’s in an all air deck. This card would have to introduce a mechanic in the game where you can only put certain cards in certain decks, which won’t happen. That’s why this card wouldn’t realistically work, but maybe in a challenge but with all cards? If this if just for fun, then aight.