I know I'm not saying anything new, but I'll add my voice to it. The clicking over and over, combined with certain units needing to target after clicking, made me feel like I was wasting 2/3 of my units. Also, the Demon levels suck at earning gold, making it a grind-fest to beat the later levels.
 "Idle Evolution"){kind=icon}
 "Heaven or Hell"){kind=icon}