mana cheat is still the biggest offender in this game by far. Kripp told them 6 years ago that it would eventually ruin ranked mode and they didn't listen.
when i don't agree with the problem of the discover mechanic per se, i also think that the random card generation has gotten so excessive, that it turns games from an actual online 1v1 card game to single player mode.
but the devs are literally incapable of grasping the core issues of hearthstone ranked mode. and while they have given up on arena mode years ago, the keep putting ranked players in this hamster wheel of releasing broken untested cards and then nerf some cards and have the game playable until the next broken deck establishes 1 week later. this repeats until the game is semi-ok to play and two weeks from then, the mini set releases and we rinse and repeat until the next expansion gets on it's way.
mana cheat, random card generation and incompetent devs. the 3 pillars of failure in hearthstone