It started with Un'Goro. We got taunts. Then it went overboard with KotFT and K&C. Instead of reactive gameplay, we now have a board full of low attack taunt minions with high defense so that it's chaotic mess everywhere. Killed Voidlord? Deal with the 3 Voidcallers that just spawned out of his butt. And then another Voidlord and then another 3 Voidcallers. Then Voidlord again with the DK effect. And so on.
Instead of making aggro decks require strategy — aggro decks such as Pirate Warriors, which taunts were made to curb — we now have control decks also requiring minimal thought: just toss a big health minion with taunt to buy time. That is to say, instead of bringing up aggro to control's level of strategic depth, we now have two dumbed down styles of play.