>>7059765The similarities to Heartcatch were pretty superficial, the artstyle and Hime being a sort of Tsubomi and Erika combo is as close as that show got to be anywhere near the level of Heartcatch.
As to why it was so hated? Probably the increased focus on romance. Yes 5 was popular despite having a major plotline revolving around the main character being in a relationship with a squirrel/her teacher, but the second half of Happiness Charge was COMPLETELY about various love stories for each character. The target audience was too young for that and the big friends don't want to see their waifus obsessing over boys or any of the emo drama that comes with it.
It didn't help that the only interesting plot to come out of any of it was Cure Unlovely, who was obviously never going to last more than 5 minutes in a single episode, because you can't have your main character go bad for any amount of time in a show like this.