Lack of reward and excessive Ad
There is Ad after every level. The game needs you to watch an Ad to open your reward box and watch another Ad to claim the reward. Basically you spend more time watching Ad than time spent playing the game. Another major problem is that the game rarely gives you gems, which means you can rarely upgrade your inventory. Even when you finally get enough gems, the chance of you getting good inventory is extremely low. After playing the game for a while you will notice that you have accumulated a lot of coins but can't spend any of it to upgrade your troops as you lack the upgrade points from the gem reward.
