When they print a really bad MtG card, I don't really care because no one will ever use it, it will be as if they never printed the card, and it won't harm general play.
When they print a bad Hearthstone card, thanks to Webspinner-Recombobulator-Shredders-Unstable Portal, it adds variance to the game that probably does more harm than good (if those cards needed risk, enough was already supplied by situational cards and battlecries). I find middle-finger-to-rexxar buzzard and Mekgineer Thermaplugg frustrating to even exist. If they were overcosted by 1 mana it'd be one thing, but being overcosted by 2 mana makes it a trivial decision to just play the other cards in your hand for the ones that go to hand, and, less often, a trivial set-in-stone game if you fizzle the straight into play ones.