Not because they aren't strong enough to keep up, but because the wording on the cards directly conflicts with how the game is played in modern times
Durable, secure, and made to protect your phone and your card
Kardur, Doomscourge Kaldheim's demons are vicious raiders with an unrivaled thirst for destruction
While his depiction in Sun & Moon has so far been more comedic, immature and idiotic than in XY , he's managed to retain his battle competence from the latter, making him something of an Idiot Savant
Not even the epic side shot artwork of Charizard breathing fire has made this card go up to the value many fans would have expected it to be at
Obviously, if you have graveyard synergy, flashback, or cards you want to discard, the effect is all upside, but you don't have to go this far