Heavy emphasis on pay to win, having good units beats out strategy, yet higher rarity units are often trash, no pity system, outdated UI, horrible F2P premium currency drops, 0 energy refund upon losing a stage yet no way to practice said stage beforehand, no difficulty rating on any stage meaning you've got no idea if you can handle it until you start the stage wasting your energy if you fail, and abrupt difficulty spikes based on whether or not you got a good unit from whatever banner is on.