The game itself is pretty decent. Sure when the arena or whatever comes out then vip players will have huge advantage but the singleplayer part isnt half bad despite some shortcomings like extremely small energy storage or lack of system for leveling extra maidens which do not fight.
Unfortunately the devs cant make events for shit. Too much materials needed with too low drop rate and completely unnecessary delayed unlocking of later stages + lack of any kind of automation so you need to fight one stage hundreds of times manually like an idiot wasting huge amount of time.
Not to mention you dont even need any special testing. Basic math will tell you that the requirements for rewards are ridiculous...